chore(package): update mocha to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "chai": "^4.1.2",
     "coveralls": "^3.0.2",
     "istanbul": "^0.4.5",
-    "mocha": "^5.2.0",
+    "mocha": "^6.0.0",
     "mocha-lcov-reporter": "^1.3.0",
     "standard": "^12.0.1",
     "tape": "^4.9.1",