added failing test case for uninflected resource

I implemented a test case for the usage of the `ClassResourceInterface` in combination with an uninflectable word (Media).

The following class causes some problems, because both routes are generated with the exactly same route name: 

```php
<?php
namespace FOS\RestBundle\Tests\Fixtures\Controller;

use FOS\RestBundle\Controller\FOSRestController;
use FOS\RestBundle\Routing\ClassResourceInterface;

class MediaController extends FOSRestController implements ClassResourceInterface
{
    public function cgetAction()
    {} // [GET] /media

    public function getAction($slug)
    {} // [GET] /media/{slug}
} 
```

Both routes get the route name `get_media`, so that one is getting overwritten by the other. A solution would be to name the route for the collection `cget_media`, but that would possibly cause some problems, if existing users use the route name in some way, and I don't know if this is easy achieveable.