[CssSelector] added the license of the Python library we ported to PHP
Merge branch '2.3' into 2.5

* 2.3:
  [TwigBridge] fix form requirement
  [CssSelector] added the license of the Python library we ported to PHP
  [SecurityBundle] avoid unneeded work

Conflicts:
	src/Symfony/Bridge/Twig/composer.json