chore(package): update mocha to version 6.1.0

Closes #9

Author: greenkeeper[bot]

package.json

@@ -89,7 +89,7 @@
     "json-loader": "^0.5.7",
     "lint-staged": "^8.1.0",
     "mini-css-extract-plugin": "^0.5.0",
-    "mocha": "^5.2.0",
+    "mocha": "^6.1.0",
     "prettier": "^1.15.1",
     "react": "^16.6.3",
     "react-addons-test-utils": "^15.3.2",