CBLT-181:  root the doc zipfile in a dir named for the build number

Change-Id: I4ecce85eabd2ca90d028f4262c440133051ee182
Reviewed-on: http://review.couchbase.org/34409
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>