Update documentation for the ring builder

Change-Id: I10c591e7ddefeb42bd30fd0df1cce6cd99f25442
Signed-off-by: Luis Pabon <lpabon@redhat.com>
Reviewed-on: http://review.gluster.org/5959
Reviewed-by: Peter Portante <pportant@redhat.com>
Tested-by: Peter Portante <pportant@redhat.com>