Merge pull request #2821 from LLK/greenkeeper/postcss-loader-3.0.0

Update postcss-loader to the latest version 🚀

package.json

@@ -70,8 +70,9 @@
     "lodash.pick": "4.4.0",
     "minilog": "3.1.0",
     "mkdirp": "^0.5.1",
+    "postcss-import": "^11.0.0",
     "postcss-import": "^12.0.0",
-    "postcss-loader": "^2.1.4",
+    "postcss-loader": "^3.0.0",
     "postcss-simple-vars": "^4.0.0",
     "prop-types": "^15.5.10",
     "raf": "^3.4.0",