Merge pull request #325 from rezonanc/di

Include Symfony DI component

README.md

 * [Container](https://github.com/thephpleague/container) - Another flexible dependency injection container.
 * [PHP DI](http://mnapoli.github.com/PHP-DI/) - A dependency injection implementation using annotations.
 * [Acclimate](https://github.com/jeremeamia/acclimate) - A common interface to dependency injection containers and service locators.
+* [Symfony DI](https://github.com/symfony/DependencyInjection) - A Dependency Injection Container component used in Symfony.
 
 ## Imagery
 *Libraries for manipulating images.*