chore(package): update should to version 9.0.0 (#1939)

https://greenkeeper.io/ [skip ci]

Author: greenkeeperio-bot

package.json

@@ -82,7 +82,7 @@
     "recursive-readdir": "^2.0.0",
     "run-sequence": "^1.2.1",
     "shelljs": "^0.7.0",
-    "should": "^8.3.1",
+    "should": "^9.0.0",
     "yeoman-assert": "^2.0.0",
     "yeoman-test": "~1.4.0"
   },