chore(package): update mocha to version 6.1.1

Closes #24

Author: greenkeeper[bot]

package.json

@@ -36,6 +36,6 @@
     "@types/mocha": "5.2.6",
     "chai": "4.1.2",
     "lodash": "4.17.11",
-    "mocha": "6.0.0"
+    "mocha": "6.1.1"
   }
 }