chore(package): update mocha to version 6.1.2

Closes #525

Author: greenkeeper[bot]

package.json

@@ -70,7 +70,7 @@
     "jsdom": "11.5.1",
     "material-ui": "next",
     "material-ui-icons": "^1.0.0-alpha.3",
-    "mocha": "4.0.1",
+    "mocha": "6.1.2",
     "mocha-jsdom": "1.1.0",
     "pre-commit": "^1.2.2",
     "prismjs": "^1.6.0",