As this project gets bigger, the contributing guidelines may become more strict. But for now, just fork the repository and please be a good person, i.e. use your own judgement of what is appropriate, ensuring all the existing tests pass, adding some docs to your code, etc. before making a pull request.
If there are any bugs in the code or any features you want to request, please submit an appropriate issue.
Finally, I am quite new to this so if you have any suggestions for me, please contact me.