chore(package): update mocha to version 6.0.1

Closes #6

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
   "devDependencies": {
     "assume": "~1.5.0",
     "istanbul": "~0.4.5",
-    "mocha": "~3.1.2",
+    "mocha": "~6.0.1",
     "pre-commit": "~1.2.0"
   },
   "dependencies": {