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/Validator/Constraints/RoleValidator.php

@@ -19,7 +19,6 @@ use Symfony\Component\Validator\Exception\UnexpectedTypeException;
  */
 class RoleValidator extends ConstraintValidator
 {
-
     /**
      * @var string[]
      */
@@ -37,7 +36,7 @@ class RoleValidator extends ConstraintValidator
     public function validate($value, Constraint $constraint)
     {
         if (!$constraint instanceof Role) {
-            throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Role');
+            throw new UnexpectedTypeException($constraint, __NAMESPACE__ . '\Role');
         }
 
         $roles = $value;