chore(package): update mocha to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "coveralls": "^3.0.0",
     "eslint": "^4.1.0",
     "istanbul": "^0.4.1",
-    "mocha": "^3.0.0",
+    "mocha": "^4.0.0",
     "should": "^13.0.0"
   },
   "dependencies": {