Revert "Moved libuv plugin to couchnode."

This reverts commit 2974965da5a18186f46ca19ab68223f39a8eeac1.

Change-Id: I5204ad925263cbecc2b8e5c1f89515509dd92a24
Reviewed-on: http://review.couchbase.org/30490
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>