chore(package): update webpack-dev-server to version 2.4.2

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -45,6 +45,6 @@
     "tap": "^10.2.0",
     "travis-after-all": "^1.4.4",
     "webpack": "2.2.1",
-    "webpack-dev-server": "^2.4.1"
+    "webpack-dev-server": "^2.4.2"
   }
 }