Update README.rst
Update README.rst

After the patch merged(Add devstack support for senlin dashboard):
https://review.openstack.org/#/c/282138/

Change-Id: Ib075e8aee181a905e515d05a1a37ce65377bf205

openstack/senlin-dashboard,stackforge/senlin-dashboard,openstack/senlin-dashboard,stackforge/senlin-dashboard,openstack/senlin-dashboard,openstack/senlin-dashboard,stackforge/senlin-dashboard