Auto merge of #3458 - alexcrichton:docs, r=steveklabnik
authorbors <bors@rust-lang.org>
Mon, 26 Dec 2016 19:04:45 +0000 (19:04 +0000)
committerbors <bors@rust-lang.org>
Mon, 26 Dec 2016 19:04:45 +0000 (19:04 +0000)
Update README build instructions

Closes #3437


Trivial merge