Corrected sentence mentioned by @weaverryan

Author: wouterj

README.markdown

@@ -7,9 +7,10 @@ Contributing
 ------------
 
 >**Note** 
->Unless you're documenting a feature that's new to a subversion of Symfony 2, 
->all pull requests must be based off of the **2.0** branch, **not** the master
->or 2.1 branch.
+>Unless you're documenting a feature that's new to a specific version of Symfony 
+>(e.g. Symfony 2.1), all pull requests must be based off of the **2.0** branch, 
+>**not** the master or 2.1 branch.
 
 We love contributors! For more information on how you can contribute to the
-Symfony documentation, please read [Contributing to the Documentation](http://symfony.com/doc/current/contributing/documentation/overview.html) 
+Symfony documentation, please read 
+[Contributing to the Documentation](http://symfony.com/doc/current/contributing/documentation/overview.html)