chore(package): update mocha to version 6.0.2

Closes #280

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "glob": "^7.1.1",
     "http-server": "^0.11.0",
     "istanbul": "^0.4.5",
-    "mocha": "^5.0.5",
+    "mocha": "^6.0.2",
     "mocha-phantomjs-core": "^2.1.1",
     "octokat-fixtures": "git://github.com/philschatz/octokat-fixtures",
     "parallelshell": "^3.0.0",