Fix #96: CssSelector removed in symfony 3
Fix #96: CssSelector removed in symfony 3

This patch ensures `WebTestCase` is compatible with Symfony 2 and 3.

`Symfony\Component\CssSelector\CssSelector` class was removed in Symfony 3 in favor of `Symfony\Component\CssSelector\CssSelectorConverter`. In Symfony 3, the crawler automatically adds HTML support
if necessary.
atoum/AtoumBundle