Bump webpack-dev-server to version 1.15.2 to fix facebook#574 (facebook#652)

Author: dceddia

package.json

@@ -75,7 +75,7 @@
  "style-loader": "0.13.1",
  "url-loader": "0.5.7",
  "webpack": "1.13.2",
- "webpack-dev-server": "1.15.1",
+ "webpack-dev-server": "1.15.2",
  "whatwg-fetch": "1.0.0"
  },
  "devDependencies": {