chore(package): update webpack-cli to version 3.3.6

Closes #309

Author: greenkeeper[bot]

package.json

@@ -86,7 +86,7 @@
     "wdio-webpack-service": "^1.0.1",
     "webdriverio": "^4.10.2",
     "webpack": "4.7.0",
-    "webpack-cli": "^2.0.12",
+    "webpack-cli": "^3.3.6",
     "webpack-dev-middleware": "3.1.3"
   },
   "repository": {},