Laravel 5 Class 'Prettus\Repository\Providers\Repository ServiceProvider' not found

I'm study about Repository Design Pattern in laravel and i'm using http://ift.tt/1BVSE6r to do it .

But after i copy paste folder prettus in my project and add in my config/app.php Prettus\Repository\Providers\RepositoryServiceProvider::class to the end of the providers array .

I have some problem . Class 'Prettus\Repository\Providers\Repository ServiceProvider' not found

After that project can't run . I don't know why . Please help me

Thanks

via Chebli Mohamed