chore(package): update mocha to version 6.2.1

Closes #7

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "karma-opera-launcher": "^1.0.0",
     "karma-safari-launcher": "^1.0.0",
     "karma-sauce-launcher": "^1.0.0",
-    "mocha": "^3.0",
+    "mocha": "^6.2.1",
     "watchify": "^3.7.0"
   },
   "license": "MIT",