chore(package): update postcss to version 5.2.5 (#167)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -26,7 +26,7 @@
     "nprogress": "0.2.0",
     "onmount": "1.3.0",
     "pjax": "0.2.4",
-    "postcss": "5.2.4",
+    "postcss": "5.2.5",
     "pug": "2.0.0-beta6",
     "stylus": "0.54.5",
     "uglifyify": "3.0.3",