Fix the format of README.rst for devstack
Fix the format of README.rst for devstack

Change-Id: I8eb82e985a622e802cc4b15a0b60442d782d0064
Closes-bug: 1529210

openstack/networking-odl,FedericoRessi/networking-odl,openstack/networking-odl,FedericoRessi/networking-odl,openstack/networking-odl,flavio-fernandes/networking-odl,flavio-fernandes/networking-odl