chore(package): update mocha to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
   "devDependencies": {
     "chai": "^4.0.1",
     "gulp": "^3.9.1",
-    "mocha": "^3.3.0",
+    "mocha": "^4.0.0",
     "stream-assert": "^2.0.3"
   }
 }