chore(package): update gulp-mocha to version 4.1.0

Closes #8

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "gulp": "^3.9.0",
     "gulp-babel": "^6.1.1",
     "gulp-eslint": "^3.0.1",
-    "gulp-mocha": "^3.0.1",
+    "gulp-mocha": "^4.1.0",
     "gulp-util": "^3.0.7",
     "gulp-watch": "^4.3.5",
     "mocha": "^3.1.2",