chore(package): update mocha to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "jsdom": "^12.0.0",
     "jsdom-global": "^3.0.2",
     "load-grunt-tasks": "^4.0.0",
-    "mocha": "^5.0.0",
+    "mocha": "^6.0.0",
     "nyc": "^12.0.1",
     "unexpected": "^10.13.3"
   },