Symfony2 tutorial: Twig extensions and dependency injection

http://lrotherfield.com/blog/symfony2-tutorial-twig-extensions-and-dependency-injection/

Symfony2 Reverse Proxy Cache Invalidation

http://symfony.com/doc/current/book/http_cache.html#cache-invalidation http://showmethecode.es/php/symfony/symfony2-reverse-proxy-borrar-la-cache-de-una-url/

How to use and Register namespaced Twig Paths

http://symfony.com/doc/current/cookbook/templating/namespaced_paths.html