Release plovr version

Hello @nicks, 

Please review the following commits I made in branch 'nick-closure'.

7f01f9831b819dd193c7ff834a971f8032e2dff8 (2013-12-17 12:28:03 -0500)
Release plovr version

a38f330c6a5239ac4461310b3a2ab449840807b0 (2013-12-17 12:16:29 -0500)
Bump closure version

R=@nicks