Update Webpack to fix source map issues (react#1188)

Author: gaearon

packages/react-scripts/package.json

@@ -66,7 +66,7 @@
     "strip-ansi": "3.0.1",
     "style-loader": "0.13.1",
     "url-loader": "0.5.7",
-    "webpack": "1.13.2",
+    "webpack": "1.14.0",
     "webpack-dev-server": "1.16.2",
     "webpack-manifest-plugin": "1.1.0",
     "webpack-subresource-integrity": "0.7.0",