Added setup guides

I'd added these to [my own repo](https://github.com/obnorthrup/144coursework), but it probably makes more sense to have them on the course website. Up to you.

Were my instructions for setting up individual repos (which I added after you approved the guide) okay? This morning I wondered whether perhaps you'd wanted everyone to actually fork your repo and submit HW via pull requests instead.

Speaking of which, this is my first pull request ever, so please let me know if I'm doing it wrong.