Update CONTRIBUTING.md

Author: willdurand

CONTRIBUTING.md

@@ -1,9 +1,10 @@
 Contributing
 ============
 
-First of all, thank you for contributing, you are awesome! Here are a few rules
-to follow in order to ease code reviews, and discussions before maintainers
-accept and merge your work.
+First of all, **thank you** for contributing, **you are awesome**!
+
+Here are a few rules to follow in order to ease code reviews, and discussions before
+maintainers accept and merge your work.
 
 You MUST follow the [PSR-1](http://www.php-fig.org/psr/1/) and
 [PSR-2](http://www.php-fig.org/psr/2/). If you don't know about any of them, you