Compatibility with Symfony 2.3

[KeKs0r]

I wanted to upgrade my project to Symfony 2.3 but, the due to the requirement of

symfony/framework-bundle: >=2.0,<2.3-dev

there is no available 2.3 package.
Composer.json should be adapted.

[stephpy]

I updated composer.json to 2.*.

Thanks.