PYCBC-119: Add bucket property

Change-Id: I37be64714781e6576d8982f9e8525ed886db8488
Reviewed-on: http://review.couchbase.org/26399
Reviewed-by: Mordechai Nunberg <mnunberg@haskalah.org>
Tested-by: Mordechai Nunberg <mnunberg@haskalah.org>