fix(package): update commander to version 4.1.1

Closes #10

Author: greenkeeper[bot]

package.json

@@ -9,7 +9,7 @@
   "dependencies": {
     "async": "^2.1.4",
     "colors": "^1.1.2",
-    "commander": "^2.9.0",
+    "commander": "^4.1.1",
     "lodash": "^4.17.2",
     "readdir": "^0.0.13",
     "semver": "^5.0.3"