Migrate .testenv rules and adopt Galaxy linting

[karras]

We should consider using the Ansible Galaxy YAML linting rules as our base rules and extend them if necessary:

https://github.com/ansible/galaxy/blob/devel/galaxy/importer/linters/yamllint.yaml
https://galaxy.ansible.com/docs/contributing/content_scoring.html

At the moment this repo only contains ansible-lint rules. How about managing the ansible-lint as well as yamllint rules in here and clone this repo in all Travis builds. This way we can also get rid of the static .testenv repo which has to be maintained individually at the moment.