improved code styles #158 (#172)

* use php-cs-fixer instead of phpcodesniffer
* updated scrutinizer config
* adjusted code yules to all files
* updated CONTRIBUTING guidelines

src/Event/ConfigureMenuEvent.php

@@ -12,7 +12,6 @@ namespace App\Event;
 use Avanzu\AdminThemeBundle\Event\SidebarMenuEvent;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\EventDispatcher\Event;
-use Symfony\Component\Security\Core\Authorization\AuthorizationChecker;
 
 /**
  * The ConfigureMenuEvent is used for populating navigations.