replace Symfony2 with Symfony

Author: dbu

Diff for: CONTRIBUTING.md

@@ -1,8 +1,8 @@
 Contributing
 ------------
 
-Symfony2 CMF is an open source, community-driven project. We follow the same
-guidelines as core Symfony2. If you'd like to contribute, please read the
+Symfony CMF is an open source, community-driven project. We follow the same
+guidelines as core Symfony. If you'd like to contribute, please read the
 [Contributing Code][1] part of the documentation. If you're submitting a pull
 request, please follow the guidelines in the [Submitting a Patch][2] section
 and use the [Pull Request Template][3].