Spanish locale

To have the login in spanish you can change the array in sfFacebook::getLocale from:

```
    $culture_to_locale = array(
      'fr' => 'fr_FR',
      'en' => 'en_US',
      'de' => 'de_DE',
      'it' => 'it_IT',
    );
```

to:

```
    $culture_to_locale = array(
      'fr' => 'fr_FR',
      'en' => 'en_US',
      'de' => 'de_DE',
      'it' => 'it_IT',
      'es' => 'es_ES',
    );
```
