Remove fork content

[smangham]

The material is already a bit cramped, forks are too much and they make the mini-project harder to do as people open issues on the wrong repo, needing to turn on issues is a pain, and pull targets differ. Replace with templating.

[smangham]

Drop it entirely, add more bad files to the climate-analysis template and use that for the mini-project bit. Create a new version of the base git repo that has more bad files in and get people to start from that template.

[smangham]

OK, actually editing the climate-analysis template is bad because then people using it in just the intro to git section get garbage code. We want to just make a new, bad template. We'd lose the poor quality commit messages, but... that's enough.