Add missing webpack-dev-server devDependency

Author: jaythomas

package.json

@@ -45,7 +45,8 @@
     "karma-firefox-launcher": "^1.0.0",
     "karma-ie-launcher": "^1.0.0",
     "karma-jasmine": "^1.1.0",
-    "webpack": "^1.14.0"
+    "webpack": "^1.14.0",
+    "webpack-dev-server": "^2.4.5"
   },
   "keywords": [
     "angular",