Allow to use CouchbaseMock for tests

This currently relies on a version of CouchbaseMock still in
development; nevertheless these are the Python bits required

Binary may be found in the URL provided in the sample file
Change-Id: I0cdc638bc528e7547b9c81b6a7c404974b384715
Reviewed-on: http://review.couchbase.org/27478
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>