Update webpack to 2.6.1 (#2383)

Author: gaearon

packages/react-scripts/package.json

@@ -50,7 +50,7 @@
     "source-map-loader": "^0.2.1",
     "sw-precache-webpack-plugin": "0.9.1",
     "url-loader": "0.5.8",
-    "webpack": "2.6.0",
+    "webpack": "2.6.1",
     "webpack-dev-server": "2.4.5",
     "webpack-manifest-plugin": "1.1.0",
     "whatwg-fetch": "2.0.3"