Merge pull request #6 from PolymerX/greenkeeper/postcss-6.0.13

Update postcss to the latest version 🚀

Author: LasaleFamine

package.json

@@ -55,7 +55,7 @@
     "fs-extra": "4.0.2",
     "loader-utils": "1.1.0",
     "parse5": "3.0.2",
-    "postcss": "6.0.12",
+    "postcss": "6.0.13",
     "postcss-load-config": "1.2.0"
   },
   "devDependencies": {