fix(package): update commander to version 5.1.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
   "dependencies": {
     "co": "^4.6.0",
     "colors": "^1.3.3",
-    "commander": "^4.0.0",
+    "commander": "^5.1.0",
     "moment": "^2.23.0",
     "shelljs": "^0.8.3"
   }