Auto merge of #4465 - matklad:yak-shaving, r=alexcrichton
authorbors <bors@rust-lang.org>
Sun, 3 Sep 2017 20:59:43 +0000 (20:59 +0000)
committerbors <bors@rust-lang.org>
Sun, 3 Sep 2017 20:59:43 +0000 (20:59 +0000)
Add CONTRIBUTING.md

r? @alexcrichton


Trivial merge