Made it possible to change the Symfony version locally

Author: stof

vendor/vendors.php

@@ -12,6 +12,10 @@
 
 set_time_limit(0);
 
+if (isset($argv[1])) {
+    $_SERVER['SYMFONY_VERSION'] = $argv[1];
+}
+
 $vendorDir = __DIR__;
 $deps = array(
     array('symfony', 'http://github.com/symfony/symfony', isset($_SERVER['SYMFONY_VERSION']) ? $_SERVER['SYMFONY_VERSION'] : 'origin/master'),