/**
  * Renvoie une instance de la classe
  * @author Alban Truc
  * @since 30/01/14
  * @return mixed
  */
 public static function instantiate()
 {
     if (!isset(self::$instance)) {
         $class = __CLASS__;
         self::$instance = new $class();
     }
     return self::$instance;
 }