chore(package): update mocha to version 6.1.2

Closes #4

package.json

@@ -35,7 +35,7 @@
     "assume": "~1.5.0",
     "bigpipe": "~0.9.12",
     "istanbul": "~0.4.5",
-    "mocha": "~3.1.2",
+    "mocha": "~6.1.2",
     "pre-commit": "~1.2.0"
   }
 }