auto merge of #9236 : steveklabnik/rust/rustpkg_init, r=catamorphism
Closes #9045
Built on top of #9235, which isn't strictly needed for now, but I imagine I will use part of. Unsure.
I mostly wanted to start this off to get some feedback from @catamorphism and others. These are the directories that actually need made, but I was thinking about adding a few other things:
1. an `examples` directory, since it seems like that's a common pattern
2. a `.gitignore` file that ignores `build`. And anything else that makes sense
3. a sample module that'd actually compile
projects / rust.git / commit