chore(package): update mocha to version 6.1.1

Closes #18

Author: greenkeeper[bot]

package.json

@@ -36,6 +36,6 @@
     "coffee-script": "^1.10.0",
     "js-yaml": "~3.10.0",
     "fbp": "^1.5.0",
-    "mocha": "^5.0.0"
+    "mocha": "^6.1.1"
   }
 }