chore(package): update mocha to version 6.2.1

Closes #27

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "eslint": "^5.0.0",
     "istanbul": "^0.4.5",
     "jsdoc": "^3.4.3",
-    "mocha": "^5.0.0",
+    "mocha": "^6.2.1",
     "sinon": "^5.0.0",
     "webpack": "^4.0.0"
   }