Bump PostCSS version.

Author: timdorr

package.json

@@ -34,7 +34,7 @@
   },
   "homepage": "https://github.com/css-modules/postcss-modules-extract-imports",
   "dependencies": {
-    "postcss": "^4.1.11"
+    "postcss": "^5.0.4"
   },
   "devDependencies": {
     "babel": "^5.4.7",