Store the user items selection on cookie

This PR is related to issue #20 and it's working in progress because I need create tests.

![fm-store-user-selection-on-cookie](https://cloud.githubusercontent.com/assets/1503773/5240038/d22f5c08-78e0-11e4-8211-df980d113047.gif)
This step is necessary to match the correct routes using ```resources```.
If you don't put this, the submit in variant class is executed class_controller instead of variant_class_controller.