Auto merge of #4559 - derekdreery:add_docs, r=alexcrichton
authorbors <bors@rust-lang.org>
Tue, 3 Oct 2017 09:18:58 +0000 (09:18 +0000)
committerbors <bors@rust-lang.org>
Tue, 3 Oct 2017 09:18:58 +0000 (09:18 +0000)
Add some more docs

Add some more docs for various parts of cargo, and add/improve a few debug implementations.


Trivial merge