chore(package): update mocha to version 6.2.1

Closes #67

Author: greenkeeper[bot]

package.json

@@ -76,7 +76,7 @@
     "karma-sourcemap-loader": "0.3.7",
     "karma-webpack": "1.8.0",
     "mkdirp": "0.5.1",
-    "mocha": "3.2.0",
+    "mocha": "6.2.1",
     "nyc": "10.0.0",
     "phantomjs-prebuilt": "2.1.14",
     "rimraf": "2.5.4",