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)
Of course will replace. You are replacing the entire hash with that code.

You should instead:

```
character_sheet  = JSON.parse(cookies[:character_sheet])
character_sheet[:race_variant_slug] = params[:race_varian_slug]
cookies[:carachter_sheet] = character_sheet.to_json
```