chore(package): update mocha to version 5.1.1

Closes #32

Author: greenkeeper[bot]

package.json

@@ -40,6 +40,6 @@
     "coveralls-send": "0.0.2",
     "istanbul": "^0.4.5",
     "jshint": "^2.9.1",
-    "mocha": "^3.2.0"
+    "mocha": "^5.1.1"
   }
 }