fix(package): update commander to version 4.0.0

Closes #9

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "node": ">=8"
   },
   "dependencies": {
-    "commander": "2.19.0",
+    "commander": "4.0.0",
     "dateformat": "3.0.3",
     "fs-extra": "7.0.1",
     "rc": "1.2.8",