improved code styles #158 (#172)

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

tests/Controller/SidebarControllerTest.php

@@ -15,7 +15,6 @@ namespace App\Tests\Controller;
  */
 class SidebarControllerTest extends ControllerBaseTest
 {
-
     public function testIsSecure()
     {
         $this->markTestSkipped('no public route available');