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)
I don't know what is your editor, but if you are using sublime, you can configure this option to avoid this warning:

```
"ensure_newline_at_eof_on_save": true,
```