Merge pull request #685 from LLK/greenkeeper/postcss-import-11.0.0

Update postcss-import to the latest version 

package.json

@@ -62,7 +62,7 @@
     "lodash.pick": "4.4.0",
     "minilog": "3.1.0",
     "mkdirp": "^0.5.1",
-    "postcss-import": "^10.0.0",
+    "postcss-import": "^11.0.0",
     "postcss-loader": "^2.0.5",
     "postcss-simple-vars": "^4.0.0",
     "prop-types": "^15.5.10",