APP_INCLUDE should point to bootstrap.php.cache

I just found out that it is wrong to use `vendor/autoload.php` as the `APP_INCLUDE` environment parameter for PHP Resque.

We have to use `app/autoload.php` because this one also initializes the `AnnotationRegistry` autoloader.

I got stuck with this error:
````
[Semantical Error] The annotation "@Doctrine\ORM\Mapping\Index" in class AppBundle\Entity\Message does not exist, or could not be auto-loaded.
````