chore(package): update mocha to version 5.1.0

Closes #14

Author: greenkeeper[bot]

package.json

@@ -37,6 +37,6 @@
     "coveralls": "^2.11.6",
     "eslint": "^3.0.0",
     "istanbul": "^0.4.1",
-    "mocha": "^3.0.2"
+    "mocha": "^5.1.0"
   }
 }