Update contributing

CONTRIBUTING.md

@@ -16,14 +16,9 @@ You can now run Composer by executing the `bin/composer` script: `php /path/to/c
 Contributing policy
 -------------------
 
-All code contributions - including those of people having commit access -
-must go through a pull request and approved by a core developer before being
-merged. This is to ensure proper review of all the code.
-
 Fork the project, create a feature branch, and send us a pull request.
 
 To ensure a consistent code base, you should make sure the code follows
-the [Coding Standards](http://symfony.com/doc/current/contributing/code/standards.html)
-which we borrowed from Symfony.
+the [PSR-2 Coding Standards](http://www.php-fig.org/psr/psr-2/).
 
 If you would like to help, take a look at the [list of issues](http://github.com/composer/composer/issues).