update grunt-autoprefixer version

Author: onokumus

package.json

@@ -42,7 +42,7 @@
     "assemble": "^0.16.2",
     "css-flip": "^0.5.0",
     "grunt": "^1.0.1",
-    "grunt-autoprefixer": "^2.1.0",
+    "grunt-autoprefixer": "^3.0.4",
     "grunt-banner": "^0.3.1",
     "grunt-contrib-clean": "^0.6.0",
     "grunt-contrib-concat": "^0.5.0",