fix(package): update commander to version 4.0.1

Closes #124

Author: greenkeeper[bot]

package.json

@@ -47,7 +47,7 @@
     "rimraf": "^3.0.0"
   },
   "dependencies": {
-    "commander": "^2.9.0",
+    "commander": "^4.0.1",
     "cross-spawn": "^6.0.5",
     "debug": "^4.1.1",
     "mkdirp": "^0.5.1",