chore(package): update mocha to version 6.0.1

Closes #122

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "chai": "*",
     "eslint": "^4.19.1",
     "istanbul": "*",
-    "mocha": "4.0.0",
+    "mocha": "6.0.1",
     "q": "^1.5.0",
     "xunit-file": "*"
   },