Merge pull request sonata-project#185 from Bladrak/contributing

Added CONTRIBUTING.md file

CONTRIBUTING.md

@@ -0,0 +1,37 @@
+Sonata respects the symfony’s conventions about contributing to the code. So before going further please review the [contributing documentation of Symfony](http://symfony.com/doc/current/contributing/code/patches.html#make-a-pull-request).
+
+## Reporting bugs
+
+If you happen to find a bug, we kindly request you to report it. However, before submitting it, please:
+
+  * Check the [project documentation available online](http://sonata-project.org/bundles/)
+
+Then, if it appears that it’s a real bug, you may report it using Github by following these 3 points:
+
+  * Check if the bug is not already reported!
+  * A clear title to resume the issue
+  * A description of the workflow needed to reproduce the bug,
+
+> _NOTE:_ Don’t hesitate giving as much information as you can (OS, PHP version extensions …)
+
+## Sending a Pull Request
+
+When you send a PR, just make sure that:
+
+* You add valid test cases.
+* Tests are green.
+* The related documentation is up-to-date.
+* Also don't forget to add a comment when you update a PR with a ping to the maintainer (``@username``), so he/she will get a notification.
+
+## Contributing to the documentation
+
+You need to install the python tool to check and validate the sphinx syntax:
+
+    pip install -r Resources/doc/requirements.txt
+
+and you can check the documentation with the command:
+
+    cd Resources/doc/
+    rm -rf _build && sphinx-build -W -b html -d _build/doctrees   . _build/html
+
+The html will be available in the ``_build/html`` folder.