Ansible-review

* Don't depend on an RC version of ansible-lint. We rely on
ansible-lint 3.4.1+ because that allows matchplay to be
run against non-playbook files (should probably be renamed!)

* Ensure inventory scripts are detected as code
* Add `ansible_min_version` declaration
* Call unversioned checks Best Practice rather than Future Standard
* Move `yaml_rolesfile` and `yaml_form_rather_than_key_value` checks
inside ansible-review
* Update standards and add new ansible-lint rules to back them.
* Allow ansible-review to run from example standards and rules by
default

* Add `importlib` as dependency

* Make `repeated_vars` actually work
* Create `Makefile` classification
* Enable filtering of standard rules to run with `-s`

* Fix mis-classification of files with .yml suffix

* Add check for competing group variables