Doc update and simple fixes

[nembery]

in order to build the first example 'config/instances.yaml' I had to make these edits. With this PR the following command successfully built a single node k8 cluster w/ contrail

ansible-playbook -e orchestrator=kubernetes -i inventory/ playbooks/install_contrail.yml

I also updated the README to reflect the fact that orchestrator=none doesn't actually work and in fact needs to be kubernetes, openstack, or possibly vcenter, but none def does not work.

If there is a different preferred way to relay this info as opposed to PR, just let me know

[Andrey-mp]

commits are forbidden for this repo via pull requests. please use review.opencontrail.org