fix(package): update ws to version 4.1.0

Closes #9

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
     "test": "make check"
   },
   "dependencies": {
-    "ws": "^2.3.1"
+    "ws": "^4.1.0"
   },
   "devDependencies": {
     "chai": "^3.5.0",