Make a top level contrib doc header
Make a top level contrib doc header

This is to just make it clear that there are other resources
besides Rackspace ones.

This is not really a bug as both the rackspace and docker
headings are the same level, but when going to the page it
is easy to see why the bug was made.

Change-Id: I76a8bcf63b7c976c4fcf0baecfd58e5fcbb65d96
Fixes-bug: #1311565

noironetworks/heat,noironetworks/heat,miguelgrinberg/heat,cwolferh/heat-scratch,dragorosson/heat,takeshineshiro/heat,steveb/heat,pshchelo/heat,openstack/heat,cryptickp/heat,gonzolino/heat,cwolferh/heat-scratch,jasondunsmore/heat,takeshineshiro/heat,miguelgrinberg/heat,dims/heat,maestro-hybrid-cloud/heat,rh-s/heat,cryptickp/heat,rh-s/heat,maestro-hybrid-cloud/heat,redhat-openstack/heat,steveb/heat,dims/heat,pratikmallya/heat,dragorosson/heat,redhat-openstack/heat,srznew/heat,rdo-management/heat,openstack/heat,jasondunsmore/heat,rdo-management/heat,pratikmallya/heat,pshchelo/heat,gonzolino/heat,srznew/heat