chore(package): update mocha to version 6.0.2

Closes #93

Author: greenkeeper[bot]

package.json

@@ -61,7 +61,7 @@
     "eslint": "^4.1.0",
     "eslint-plugin-flowtype": "^2.29.2",
     "flow-bin": "^0.61.0",
-    "mocha": "^5.0.0",
+    "mocha": "^6.0.2",
     "nyc": "^11.0.1",
     "postcss": "^6.0.7",
     "postcss-modules": "^1.0.0",