Implement CI tests for ansible

[SuperQ]

Some CI testing suggestions from @paulfantom

ansible-lint -x ANSIBLE0006,ANSIBLE0010,ANSIBLE0013,ANSIBLE0016 ansible/playbooks/site.yml
ansible-playbook -i hosts ansible/playbooks/site.yml

And after conference it could be expanded to have better coverage (maybe based on molecule).
Note: Second command needs to decrypt secrets.yml and that's why I suggest to use travis as they have a good policy around such things.

[paulfantom]

Ansible needs to know all variables before running playbooks and tests. This means either:

1. decrypting secrets.yml before running tests suite
2. creating fake, unencrypted secrets.yml files for testing

Just to be on a safe side I would recommend going with second option.

[SuperQ]

CI is enabled, and our first test is a simple run of yamllint. #215

[SuperQ]

Added the ansible-lint testing here: #218.