Add support for Symfony 3.0

[robholmes]

Currently the composer.json requires "symfony/framework-bundle": "~2.3", it seems that everyone else is adding this |~3.0 to their requirements, resulting in: "symfony/framework-bundle": "~2.3|~3.0"

[arodiss]

Thank you @robholmes I checked briefly and looks like indeed bundle does not rely on anything deprecated, so I merged your PR

[robholmes]

Thanks @arodiss