Add scripts for size-weighted rebalance.

Change-Id: I04197e54fef2ff7b61fbee21ab837219354184f1
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/3573
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>