This uses hardcoded rubocop_defaults to build a minimal .rubocop.yml
config. The configuration is minimal (only list what you want), and can
be easily overridden.

The profile_builder.rb script can help in rebuilding the rubocop_defaults
file for new rubocop versions.

The cleanup_cops.yml contains a list of basic cops everyone should check.
This was originally derived from the main PDK rubocop configuration.
See https://github.com/puppetlabs/pdk/pull/78.

Downstream users can choose from four different strictness
profiles: off, cleanups_only, strict, hardcore.

* off: no cops enabled, use at your own risk.
* cleanups_only: a set of uncontroversial cops that will cleanup your
  codebase nicely. All of them have autocorrect enabled and are safe to
  apply.
* strict: the default. A good mix of cops following the established best
  practices of the community. The work required to pass this, will make
  your code base so much better.
* hardcore: enables all rubocop default cops. Still uses the recommended
  configs from strict, but enabled additional, unvetted tests. Have fun!