chore(package): update mocha to version 6.0.1

Closes #244

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "eslint-watch": "2.1.14",
     "in-publish": "2.0.0",
     "jsdom": "9.9.0",
-    "mocha": "3.2.0",
+    "mocha": "6.0.1",
     "npm-run-all": "3.1.2",
     "nyc": "^10.0.0",
     "prop-types": "^15.5.8",