Auto merge of #4170 - alexcrichton:beta-next2, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 14 Jun 2017 23:19:08 +0000 (23:19 +0000)
committerbors <bors@rust-lang.org>
Wed, 14 Jun 2017 23:19:08 +0000 (23:19 +0000)
[beta] Preserve `package.metadata` when packaging

Now that we use Serde this is actually trivial to implement!

Closes #4142


Trivial merge