chore(package): update mocha to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "chai-as-promised": "^7.1.1",
     "express": "^4.15.4",
     "fs-promise": "^2.0.3",
-    "mocha": "^3.4.2",
+    "mocha": "^4.0.0",
     "mocha-jshint": "^2.3.1",
     "rimraf": "^2.6.2",
     "temp": "^0.8.3"