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/Admin/CustomerControllerTest.php

@@ -18,7 +18,6 @@ use App\Tests\Controller\ControllerBaseTest;
  */
 class CustomerControllerTest extends ControllerBaseTest
 {
-
     public function testIsSecure()
     {
         $this->assertUrlIsSecured('/admin/customer/');