Auto merge of #4167 - alexcrichton:keep-metadata, r=matklad
authorbors <bors@rust-lang.org>
Wed, 14 Jun 2017 19:40:34 +0000 (19:40 +0000)
committerbors <bors@rust-lang.org>
Wed, 14 Jun 2017 19:40:34 +0000 (19:40 +0000)
Preserve `package.metadata` when packaging

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

Closes #4142


Trivial merge