Hello cargo

Built on top of https://github.com/rust-lang/rust/pull/15181. https://github.com/steveklabnik/rust/commit/e52719291183d7b4f691a1997c69fd75b8101b07 is the only new commit, you may want to review that separately.

I'm not sure if the car analogy is too glib.
I’d go with @huonw on this one. The *product* is capitalised, but the artefact produced is an issue. Compare with the “New issue” button in the issues list. (Sure, you’ll find plenty of counterexamples, but typically they can be attributed to title case.)