UV: Remove bufinfo

Moving to a read2 model

Change-Id: I26ac8934887d836bb51073cc32e66f5e33d7c6ac
Reviewed-on: http://review.couchbase.org/35878
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>