====== Dependency Injection ======

  * https://github.com/orno/di
  * http://framework.zend.com/manual/2.0/en/modules/zend.di.introduction.html
  * http://php-di.org/ (https://github.com/mnapoli/PHP-DI)
  * https://github.com/TomBZombie/Dice
  * https://github.com/auraphp/Aura.Di