README: quick note about roadmap.
README: quick note about roadmap.

Signed-off-by: Emilien Macchi <d605a501dec15c980af71d9dfebf4b595ab6da1f@enovance.com>

openstack/puppet-trove,egafford/puppet-trove,openstack/puppet-trove,ramsateesh/puppet-trove,egafford/puppet-trove,redhat-cip/puppet-trove,rdo-puppet-modules/puppet-trove,redhat-cip/puppet-trove,gwdg/puppet-trove,gwdg/puppet-trove,rdo-puppet-modules/puppet-trove,ramsateesh/puppet-trove,openstack/puppet-trove