fix(package): update commander to version 5.1.0

Closes #69

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
   "license": "MIT",
   "dependencies": {
     "chalk": "^2.0.1",
-    "commander": "^4.0.0",
+    "commander": "^5.1.0",
     "deep-assign": "^3.0.0",
     "fallback-cli": "^2.0.2",
     "update-notifier": "^4.0.0"