chore(package): update mocha to version 5.1.1

Closes #14

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
     "chai": "^4.0.0",
     "eslint": "^4.1.0",
     "memory-fs": "^0.4.1",
-    "mocha": "^3.2.0",
+    "mocha": "^5.1.1",
     "nyc": "^11.0.2",
     "webpack": "^3.1.0"
   },