overhaul CONTIRIBUTING.md

Thanks to #1322

Author: Byron

CONTRIBUTING.md

@@ -1,11 +1,10 @@
-### How to contribute
+# How to contribute
 
 The following is a short step-by-step rundown of what one typically would do to contribute.
 
-* [fork this project](https://github.com/gitpython-developers/GitPython/fork) on GitHub.
-* For setting up the environment to run the self tests, please look at `.travis.yml`.
-* Please try to **write a test that fails unless the contribution is present.**
-* Try to avoid massive commits and prefer to take small steps, with one commit for each.
-* Feel free to add yourself to AUTHORS file.
-* Create a pull request.
-
+- [fork this project](https://github.com/gitpython-developers/GitPython/fork) on GitHub.
+- For setting up the environment to run the self tests, please run `init-tests-after-clone.sh`.
+- Please try to **write a test that fails unless the contribution is present.**
+- Try to avoid massive commits and prefer to take small steps, with one commit for each.
+- Feel free to add yourself to AUTHORS file.
+- Create a pull request.