chore(package): update mocha to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "coveralls": "^3.0.0",
     "inspect-process": "^0.5.0",
     "istanbul": "^0.4.5",
-    "mocha": "^5.0.0",
+    "mocha": "^6.0.0",
     "nyc": "^13.2.0",
     "standard": "^12.0.0"
   },