Autoprefixer moved to postcss-cli, limit version for now to keep autoprefixer binary.

package.json

@@ -1,7 +1,7 @@
 {
   "private": true,
   "dependencies": {
-    "autoprefixer": ">= 3.1.0",
+    "autoprefixer": ">= 3.1.0 <= 5.2.1",
     "po2json": ">= 0.4.1",
     "jshint": ">= 2.5.5"
   }