chore(package): update mocha to version 4.1.0

Closes #13

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
   "devDependencies": {
     "browserify": "^14.0.0",
     "expect.js": "^0.3.1",
-    "mocha": "^3.0.2"
+    "mocha": "^4.1.0"
   },
   "dependencies": {
     "is-plain-object": "^2.0.1"