chore(package): update mocha to version 4.0.1

Closes #51

Author: greenkeeper[bot]

package.json

@@ -48,7 +48,7 @@
     "coveralls": "^2.11",
     "eslint": "^4.0",
     "istanbul": "^0.4",
-    "mocha": "^3.5",
+    "mocha": "^4.0.1",
     "mocha-lcov-reporter": "^1.2.0",
     "react": "^16.0",
     "react-dom": "^16.0"