CDB-764: use couchdbx-app from 2.0.1 branch

Change-Id: I95add5f2d31c987a9b10aafdddd5ac536fb3297e
Reviewed-on: http://review.couchbase.org/23856
Reviewed-by: Farshid Ghods <farshid@couchbase.com>
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>