Added PHP-CS-Fixer configuration file

.php_cs

@@ -0,0 +1,12 @@
+<?php
+// PHP Coding Standards Fixer
+// For more information see https://github.com/FriendsOfPHP/PHP-CS-Fixer
+
+$finder = Symfony\CS\Finder\DefaultFinder::create()
+    ->in(__DIR__ . '/src')
+;
+
+return Symfony\CS\Config\Config::create()
+    ->level(Symfony\CS\FixerInterface::PSR2_LEVEL)
+    ->finder($finder)
+;