chore(dev-server): add webpack-dev-server dependency

Author: emyann

package.json

@@ -33,7 +33,8 @@
     "tslint-loader": "^2.1.5",
     "typescript": "^2.0.0",
     "typings": "^1.3.2",
-    "webpack": "^2.1.0-beta.20"
+    "webpack": "^2.1.0-beta.20",
+    "webpack-dev-server": "^1.15.0"
   },
   "dependencies": {
     "lodash": "^4.14.1"