chore(package): update mocha to version 6.1.2

Closes #76

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
     "grunt-mocha-phantomjs": "^4.0.0",
     "grunt-mocha-test": "^0.13.2",
     "grunt-noflo-browser": "^1.5.0",
-    "mocha": "^5.0.0"
+    "mocha": "^6.1.2"
   },
   "noflo": {
     "icon": "github"