chore(package): update mocha to version 4.1.0

Closes #27

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "coveralls": "^2.11.6",
     "eslint": "^3.0.0",
     "istanbul": "^0.4.1",
-    "mocha": "^3.0.2",
+    "mocha": "^4.1.0",
     "mock-require": "^2.0.0",
     "nock": "^9.0.0",
     "promise-delay": "^2.1.0"