Update css loader (facebook#1057)

* Update css-loader to 0.26.0

* Update the production webpack config

Author: nhajidin

Diff for: packages/react-scripts/package.json

@@ -35,7 +35,7 @@
     "chalk": "1.1.3",
     "connect-history-api-fallback": "1.3.0",
     "cross-spawn": "4.0.2",
-    "css-loader": "0.25.0",
+    "css-loader": "0.26.0",
     "detect-port": "1.0.1",
     "dotenv": "2.0.0",
     "eslint": "3.8.1",