auto merge of #321 : alexcrichton/cargo/issue-304, r=wycats
authorbors <bors@rust-lang.org>
Wed, 6 Aug 2014 19:10:27 +0000 (19:10 +0000)
committerbors <bors@rust-lang.org>
Wed, 6 Aug 2014 19:10:27 +0000 (19:10 +0000)
The lockfile should only be checked in for bins, not libs.

Closes #304


Trivial merge