chore(package): update mocha to version 6.1.1

Closes #9

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "babel-cli": "^6.26.0",
     "babel-preset-es2015": "^6.24.1",
     "eslint": "^5.0.0",
-    "mocha": "^5.2.0",
+    "mocha": "^6.1.1",
     "should": "^13.2.1"
   }
 }