fix(package): update commander to version 4.0.0

Closes #61

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "lib": "lib"
   },
   "dependencies": {
-    "commander": "^2.19.0",
+    "commander": "^4.0.0",
     "express": "^4.16.4"
   },
   "devDependencies": {