Bump version 1.3.7

Change-Id: I6179b1d3a6dd785675e58324ad597e966a8376e7
Reviewed-on: http://review.couchbase.org/36011
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>