feat(scan): add rule directory recursive

[dclayton-godaddy]

Add the ability to lookup rules in subdirectories when using --rule-directory ./rules --rule-directory-recursive.

Parameter --rule-directory-recursive should include IAMNameRule.rb and GeneralRule.rb.

rules/
    IAM/
        IAMNameRule.rb
    GeneralRule.rb

closes #595

[dsilbergleithcu-godaddy]

This will definitely help some of our tooling! Great contribution @dclayton-godaddy!

[arothian]

Thanks for the contribution @dclayton-godaddy . Can you take a look at the rubocop failure and if possible sign the commit(s) - https://docs.github.com/articles/about-gpg/?

[dclayton-godaddy]

Thanks for the contribution @dclayton-godaddy . Can you take a look at the rubocop failure and if possible sign the commit(s) - https://docs.github.com/articles/about-gpg/?

sure. Thanks

[dclayton-godaddy]

@arothian rubocop issues have been addressed. Thank you for reviewing this change.