Auto merge of #5472 - alexcrichton:rename-rust, r=matklad
authorbors <bors@rust-lang.org>
Thu, 3 May 2018 19:39:24 +0000 (19:39 +0000)
committerbors <bors@rust-lang.org>
Thu, 3 May 2018 19:39:24 +0000 (19:39 +0000)
Rename the `rust` manifest key to `edition`

This'll hopefully jive better with the terminology of "edition" throughout the
rest of Rust!


Trivial merge