Added more information about contributing to Cuberite

CONTRIBUTING.md

@@ -1,3 +1,11 @@
+How to contribute to Cuberite
+-----------------------------
+Thank you for your interest in Cuberite. Contributing to Cuberite is easy, just fork the project on GitHub, make your changes and submit a pull request to get your code merged. That's all there is to it.
+Check out [GETTING-STARTED.md](https://github.com/cuberite/cuberite/blob/master/GETTING-STARTED.md) for more information about setting up the development environment for Cuberite, finding issues to work on, etc...
+
+If you are new to open source and/or GitHub, or just aren't sure about some details in the contribution process, here's a tutorial to get you started:
+[How to Contribute to an Open Source Project on GitHub](https://egghead.io/series/how-to-contribute-to-an-open-source-project-on-github)
+
 Code Conventions
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