Point people at github's git docs for now

We'll want to actually cover git and github in the curriculum, for sure.
For now, pointing people to the docs Github have already written should
provide at least some useful info. I've also pointed people at the IRC
channel if github's docs are insufficient.
Fix the tyop, thanks Mike
Merge pull request #91 from apeiron/topic/apeiron/git-github-docs

Point people at github's git docs for now