diff --git a/package.json b/package.json
index 71b05d9..bce5561 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "babel-plugin-transform-flow-strip-types": "^6.21.0",
     "babel-plugin-transform-object-rest-spread": "^6.20.2",
     "babel-preset-es2015": "^6.18.0",
-    "codecov": "^1.0.1",
+    "codecov": "^3.7.1",
     "eslint": "^3.13.1",
     "eslint-config-airbnb-base": "^11.0.1",
     "eslint-plugin-flowtype": "^2.29.2",
diff --git a/yarn.lock b/yarn.lock
index 79b9a75..2ceefd3 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2,6 +2,10 @@
 # yarn lockfile v1
 
 
+"@tootallnate/once@1":
+  version "1.1.2"
+  resolved "https://registry.yarnpkg.com/@tootallnate/once/-/once-1.1.2.tgz#ccb91445360179a04e7fe6aff78c00ffc1eeaf82"
+
 abab@^1.0.0:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/abab/-/abab-1.0.3.tgz#b81de5f7274ec4e756d797cd834f303642724e5d"
@@ -34,6 +38,16 @@ acorn@^4.0.1:
   version "4.0.3"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-4.0.3.tgz#1a3e850b428e73ba6b09d1cc527f5aaad4d03ef1"
 
+agent-base@5:
+  version "5.1.1"
+  resolved "https://registry.yarnpkg.com/agent-base/-/agent-base-5.1.1.tgz#e8fb3f242959db44d63be665db7a8e739537a32c"
+
+agent-base@6:
+  version "6.0.1"
+  resolved "https://registry.yarnpkg.com/agent-base/-/agent-base-6.0.1.tgz#808007e4e5867decb0ab6ab2f928fbdb5a596db4"
+  dependencies:
+    debug "4"
+
 ajv-keywords@^1.0.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-1.2.0.tgz#676c4f087bfe1e8b12dca6fda2f3c74f417b099c"
@@ -101,7 +115,7 @@ argparse@^1.0.7:
   dependencies:
     sprintf-js "~1.0.2"
 
-argv@>=0.0.2:
+argv@0.0.2:
   version "0.0.2"
   resolved "https://registry.yarnpkg.com/argv/-/argv-0.0.2.tgz#ecbd16f8949b157183711b1bda334f37840185ab"
 
@@ -700,6 +714,10 @@ balanced-match@^0.4.1:
   version "0.4.2"
   resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-0.4.2.tgz#cb3f3e3c732dc0f01ee70b403f302e61d7709838"
 
+balanced-match@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
+
 bcrypt-pbkdf@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/bcrypt-pbkdf/-/bcrypt-pbkdf-1.0.0.tgz#3ca76b85241c7170bf7d9703e7b9aa74630040d4"
@@ -729,6 +747,13 @@ brace-expansion@^1.0.0:
     balanced-match "^0.4.1"
     concat-map "0.0.1"
 
+brace-expansion@^1.1.7:
+  version "1.1.11"
+  resolved "https://registry.yarnpkg.com/brace-expansion/-/brace-expansion-1.1.11.tgz#3c7fcbf529d87226f3d2f52b966ff5271eb441dd"
+  dependencies:
+    balanced-match "^1.0.0"
+    concat-map "0.0.1"
+
 braces@^1.8.2:
   version "1.8.5"
   resolved "https://registry.yarnpkg.com/braces/-/braces-1.8.5.tgz#ba77962e12dff969d6b76711e914b737857bf6a7"
@@ -877,14 +902,15 @@ code-point-at@^1.0.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/code-point-at/-/code-point-at-1.1.0.tgz#0d070b4d043a5bea33a2f1a40e2edb3d9a4ccf77"
 
-codecov@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/codecov/-/codecov-1.0.1.tgz#97260ceac0e96b8eda8d562006558a53a139dffd"
+codecov@^3.7.1:
+  version "3.7.1"
+  resolved "https://registry.yarnpkg.com/codecov/-/codecov-3.7.1.tgz#434cb8d55f18ef01672e5739d3d266696bebc202"
   dependencies:
-    argv ">=0.0.2"
-    execSync "1.0.2"
-    request ">=2.42.0"
-    urlgrey ">=0.4.0"
+    argv "0.0.2"
+    ignore-walk "3.0.3"
+    js-yaml "3.13.1"
+    teeny-request "6.0.1"
+    urlgrey "0.4.4"
 
 colors@1.0.3:
   version "1.0.3"
@@ -972,6 +998,12 @@ debug@2.2.0, debug@~2.2.0:
   dependencies:
     ms "0.7.1"
 
+debug@4:
+  version "4.1.1"
+  resolved "https://registry.yarnpkg.com/debug/-/debug-4.1.1.tgz#3b72260255109c6b589cee050f1d516139664791"
+  dependencies:
+    ms "^2.1.1"
+
 debug@^2.1.1, debug@^2.2.0:
   version "2.3.3"
   resolved "https://registry.yarnpkg.com/debug/-/debug-2.3.3.tgz#40c453e67e6e13c901ddec317af8986cda9eff8c"
@@ -1207,10 +1239,14 @@ espree@^3.3.1:
     acorn "^4.0.1"
     acorn-jsx "^3.0.0"
 
-esprima@^2.6.0, esprima@^2.7.1:
+esprima@^2.7.1:
   version "2.7.3"
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-2.7.3.tgz#96e3b70d5779f6ad49cd032673d1c312767ba581"
 
+esprima@^4.0.0:
+  version "4.0.1"
+  resolved "https://registry.yarnpkg.com/esprima/-/esprima-4.0.1.tgz#13b04cdb3e6c5d19df91ab6987a8695619b0aa71"
+
 esprima@~3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-3.0.0.tgz#53cf247acda77313e551c3aa2e73342d3fb4f7d9"
@@ -1251,12 +1287,6 @@ exec-sh@^0.2.0:
   dependencies:
     merge "^1.1.3"
 
-execSync@1.0.2:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/execSync/-/execSync-1.0.2.tgz#1f42eda582225180053224ecdd3fd1960fdb3139"
-  dependencies:
-    temp "~0.5.1"
-
 exit-hook@^1.0.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/exit-hook/-/exit-hook-1.1.1.tgz#f05ca233b48c05d54fff07765df8507e95c02ff8"
@@ -1497,10 +1527,6 @@ graceful-fs@^4.1.2, graceful-fs@^4.1.4, graceful-fs@^4.1.6:
   version "4.1.11"
   resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.1.11.tgz#0e8bdfe4d1ddb8854d64e04ea7c00e2a026e5658"
 
-graceful-fs@~1:
-  version "1.2.3"
-  resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-1.2.3.tgz#15a4806a57547cb2d2dbf27f42e89a8c3451b364"
-
 "graceful-readlink@>= 1.0.0":
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/graceful-readlink/-/graceful-readlink-1.0.1.tgz#4cafad76bc62f02fa039b2f94e9a3dd3a391a725"
@@ -1578,6 +1604,14 @@ html-encoding-sniffer@^1.0.1:
   dependencies:
     whatwg-encoding "^1.0.1"
 
+http-proxy-agent@^4.0.0:
+  version "4.0.1"
+  resolved "https://registry.yarnpkg.com/http-proxy-agent/-/http-proxy-agent-4.0.1.tgz#8a8c8ef7f5932ccf953c296ca8291b95aa74aa3a"
+  dependencies:
+    "@tootallnate/once" "1"
+    agent-base "6"
+    debug "4"
+
 http-signature@~1.1.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/http-signature/-/http-signature-1.1.1.tgz#df72e267066cd0ac67fb76adf8e134a8fbcf91bf"
@@ -1586,6 +1620,13 @@ http-signature@~1.1.0:
     jsprim "^1.2.2"
     sshpk "^1.7.0"
 
+https-proxy-agent@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/https-proxy-agent/-/https-proxy-agent-4.0.0.tgz#702b71fb5520a132a66de1f67541d9e62154d82b"
+  dependencies:
+    agent-base "5"
+    debug "4"
+
 iconv-lite@0.4.13:
   version "0.4.13"
   resolved "https://registry.yarnpkg.com/iconv-lite/-/iconv-lite-0.4.13.tgz#1f88aba4ab0b1508e8312acc39345f36e992e2f2"
@@ -1594,6 +1635,12 @@ iconv-lite@^0.4.13:
   version "0.4.15"
   resolved "https://registry.yarnpkg.com/iconv-lite/-/iconv-lite-0.4.15.tgz#fe265a218ac6a57cfe854927e9d04c19825eddeb"
 
+ignore-walk@3.0.3:
+  version "3.0.3"
+  resolved "https://registry.yarnpkg.com/ignore-walk/-/ignore-walk-3.0.3.tgz#017e2447184bfeade7c238e4aefdd1e8f95b1e37"
+  dependencies:
+    minimatch "^3.0.4"
+
 ignore@^3.2.0:
   version "3.2.0"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.2.0.tgz#8d88f03c3002a0ac52114db25d2c673b0bf1e435"
@@ -2058,12 +2105,12 @@ js-tokens@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-2.0.0.tgz#79903f5563ee778cc1162e6dcf1a0027c97f9cb5"
 
-js-yaml@^3.5.1, js-yaml@^3.7.0:
-  version "3.7.0"
-  resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.7.0.tgz#5c967ddd837a9bfdca5f2de84253abe8a1c03b80"
+js-yaml@3.13.1, js-yaml@^3.5.1, js-yaml@^3.7.0:
+  version "3.13.1"
+  resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.13.1.tgz#aff151b30bfdfa8e49e05da22e7415e9dfa37847"
   dependencies:
     argparse "^1.0.7"
-    esprima "^2.6.0"
+    esprima "^4.0.0"
 
 jsbn@~0.1.0:
   version "0.1.0"
@@ -2318,6 +2365,12 @@ mime-types@^2.1.12, mime-types@~2.1.7:
   dependencies:
     brace-expansion "^1.0.0"
 
+minimatch@^3.0.4:
+  version "3.0.4"
+  resolved "https://registry.yarnpkg.com/minimatch/-/minimatch-3.0.4.tgz#5166e286457f03306064be5497e8dbb0c3d32083"
+  dependencies:
+    brace-expansion "^1.1.7"
+
 minimist@0.0.8, minimist@~0.0.1:
   version "0.0.8"
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-0.0.8.tgz#857fcabfc3397d2625b8228262e86aa7a011b05d"
@@ -2340,6 +2393,10 @@ ms@0.7.2:
   version "0.7.2"
   resolved "https://registry.yarnpkg.com/ms/-/ms-0.7.2.tgz#ae25cf2512b3885a1d95d7f037868d8431124765"
 
+ms@^2.1.1:
+  version "2.1.2"
+  resolved "https://registry.yarnpkg.com/ms/-/ms-2.1.2.tgz#d09d1f357b443f493382a8eb3ccd183872ae6009"
+
 mute-stream@0.0.5:
   version "0.0.5"
   resolved "https://registry.yarnpkg.com/mute-stream/-/mute-stream-0.0.5.tgz#8fbfabb0a98a253d3184331f9e8deb7372fac6c0"
@@ -2358,6 +2415,10 @@ node-emoji@^1.4.1:
   dependencies:
     string.prototype.codepointat "^0.2.0"
 
+node-fetch@^2.2.0:
+  version "2.6.0"
+  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.0.tgz#e633456386d4aa55863f676a7ab0daa8fdecb0fd"
+
 node-int64@^0.4.0:
   version "0.4.0"
   resolved "https://registry.yarnpkg.com/node-int64/-/node-int64-0.4.0.tgz#87a9065cdb355d3182d8f94ce11188b825c68a3b"
@@ -2742,7 +2803,7 @@ repeating@^2.0.0:
   dependencies:
     is-finite "^1.0.0"
 
-request@>=2.42.0, request@^2.55.0, request@^2.79.0:
+request@^2.55.0, request@^2.79.0:
   version "2.79.0"
   resolved "https://registry.yarnpkg.com/request/-/request-2.79.0.tgz#4dfe5bf6be8b8cdc37fcf93e04b65577722710de"
   dependencies:
@@ -2813,12 +2874,6 @@ rimraf@2, rimraf@^2.2.8, rimraf@^2.4.3, rimraf@^2.4.4, rimraf@^2.5.4, rimraf@~2.
   dependencies:
     glob "^7.0.5"
 
-rimraf@~2.1.4:
-  version "2.1.4"
-  resolved "https://registry.yarnpkg.com/rimraf/-/rimraf-2.1.4.tgz#5a6eb62eeda068f51ede50f29b3e5cd22f3d9bb2"
-  optionalDependencies:
-    graceful-fs "~1"
-
 run-async@^0.1.0:
   version "0.1.0"
   resolved "https://registry.yarnpkg.com/run-async/-/run-async-0.1.0.tgz#c8ad4a5e110661e402a7d21b530e009f25f8e389"
@@ -2941,6 +2996,12 @@ sshpk@^1.7.0:
     jsbn "~0.1.0"
     tweetnacl "~0.14.0"
 
+stream-events@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/stream-events/-/stream-events-1.0.5.tgz#bbc898ec4df33a4902d892333d47da9bf1c406d5"
+  dependencies:
+    stubs "^3.0.0"
+
 string-width@^1.0.1, string-width@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/string-width/-/string-width-1.0.2.tgz#118bdf5b8cdc51a2a7e70d211e07e2b0b9b107d3"
@@ -2992,6 +3053,10 @@ strip-json-comments@~2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-2.0.1.tgz#3c531942e908c2697c0ec344858c286c7ca0a60a"
 
+stubs@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/stubs/-/stubs-3.0.0.tgz#e8d2ba1fa9c90570303c030b6900f7d5f89abe5b"
+
 supports-color@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-0.2.0.tgz#d92de2694eb3f67323973d7ae3d8b55b4c22190a"
@@ -3042,11 +3107,15 @@ tar@~2.2.1:
     fstream "^1.0.2"
     inherits "2"
 
-temp@~0.5.1:
-  version "0.5.1"
-  resolved "https://registry.yarnpkg.com/temp/-/temp-0.5.1.tgz#77ab19c79aa7b593cbe4fac2441768cad987b8df"
+teeny-request@6.0.1:
+  version "6.0.1"
+  resolved "https://registry.yarnpkg.com/teeny-request/-/teeny-request-6.0.1.tgz#9b1f512cef152945827ba7e34f62523a4ce2c5b0"
   dependencies:
-    rimraf "~2.1.4"
+    http-proxy-agent "^4.0.0"
+    https-proxy-agent "^4.0.0"
+    node-fetch "^2.2.0"
+    stream-events "^1.0.5"
+    uuid "^3.3.2"
 
 test-exclude@^3.3.0:
   version "3.3.0"
@@ -3127,7 +3196,7 @@ uid-number@~0.0.6:
   version "0.0.6"
   resolved "https://registry.yarnpkg.com/uid-number/-/uid-number-0.0.6.tgz#0ea10e8035e8eb5b8e4449f06da1c730663baa81"
 
-urlgrey@>=0.4.0:
+urlgrey@0.4.4:
   version "0.4.4"
   resolved "https://registry.yarnpkg.com/urlgrey/-/urlgrey-0.4.4.tgz#892fe95960805e85519f1cd4389f2cb4cbb7652f"
 
@@ -3149,6 +3218,10 @@ uuid@^3.0.0:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/uuid/-/uuid-3.0.1.tgz#6544bba2dfda8c1cf17e629a3a305e2bb1fee6c1"
 
+uuid@^3.3.2:
+  version "3.4.0"
+  resolved "https://registry.yarnpkg.com/uuid/-/uuid-3.4.0.tgz#b23e4358afa8a202fe7a100af1f5f883f02007ee"
+
 v8flags@^2.0.10:
   version "2.0.11"
   resolved "https://registry.yarnpkg.com/v8flags/-/v8flags-2.0.11.tgz#bca8f30f0d6d60612cc2c00641e6962d42ae6881"