Added Contributing section

README.md

@@ -34,6 +34,19 @@ You can download a **ready-built** package from the [Downloads page on http://ge
 Check out the [install procedures](http://learn.getgrav.org/basics/installation) for more information.
 
 
+# Contributing
+We appreciate any contribution to Grav, whether it is related to bugs, grammar, or simply a suggestion or improvement.
+However, we ask that any contribution follow our simple guidelines in order to be properly received.
+
+All our projects follow the [GitFlow branching model][gitflow-model], from development to release. If you aren't familiar with it, there are several guides and tutorials to make you understand what it is about.
+
+You will probably want to get started by installing [this very good collection of git extensions][gitflow-extensions].
+
+What you mainly want to know is that:
+
+- All the main activity happens in the `develop` branch. Any pull-request should be addressed only to that branch. We won't consider pull-requests made to the `master`.
+- It's very well appreciated, and highly suggested, to start a new feature whenever you want to make changes or add functionalities. It will make it much easier for us to just checkout your feature branch and test it, before merging it into `develop`
+
 # Getting Started
 
 * [What is Grav?](http://learn.getgrav.org/basics/what-is-grav)
@@ -51,3 +64,7 @@ Check out the [install procedures](http://learn.getgrav.org/basics/installation)
 # License
 
 See [LICENSE](LICENSE)
+
+
+[gitflow-model]: http://nvie.com/posts/a-successful-git-branching-model/
+[gitflow-extensions]: https://github.com/nvie/gitflow