build(@angular/cli): update webpack-dev-server to satisfy peer dependency

Author: devoto13

packages/@angular/cli/package.json

@@ -85,7 +85,7 @@
     "walk-sync": "^0.3.1",
     "webpack": "~3.3.0",
     "webpack-dev-middleware": "^1.11.0",
-    "webpack-dev-server": "~2.4.5",
+    "webpack-dev-server": "~2.5.1",
     "webpack-merge": "^2.4.0",
     "zone.js": "^0.8.14"
   },