Added compatibility with Symfony 2.2.1

Hi.

Do you have any plan to upgrade bundle for compatibility with the new version of the framework?

There is conflict with: https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Routing/Loader/YamlFileLoader.php#L127

Do you prefer merge this PR or in the near future there will be a tag with full compatibility with 2.2.1 or 2.3?

Regards,
Dmitry