TMI: More rustpkg progress

Today was the beginning of the research work week here in Vancouver, and I don't know about you, but I can't follow a discussion for 8 hours straight -- even with a break for lunch in the middle. So I tried to listen as well as I could to the parts that overlapped more with my knowledge, and during the rest, hack on stuff and listen with one ear.

I started cleaning up my rustpkg changes in preparation for submitting a pull request. Part of that was adding more documentation and such, part was removing bits of code that aren't needed now that we're using package IDs and not requiring a package script. I'm not sure whether to break existing code that uses rustpkg (not that there's a lot of it yet) or try to be backwards-compatible.

After that, it'll be submitting a pull request for the changes I made to rust-sdl, making the clean command work (since it's annoying to have to manually delete files every time to make sure my changes still worked), and making rust-http-client build as my second test project. And then, of course, making all the other commands work. That's just the beginning.

Figuring out how to write unit tests for rustpkg will be interesting as well. Necessary, but I'm not sure how.