Lintly

* Add support for Python 3.9
* Upgrade `click` version requirements
* Fixed an issue preventing Lintly from submitting a review when there are 51+ review comments

* **Backward Incompatible**: Change the default format from "unix" to "flake8."
This has no functional difference, as they're the same format. However, it
will result in a different GitHub commit status context, which could prevent
you from merging PRs if the unix commit status is required by repo settings.
* Add support for GitHub Checks when called from GitHub Actions with the `--use-checks` flag.
* Add support for posting PR reviews that approve or request changes with the `--request-changes` flag.
* Update PR review comments to link to Lintly repo.
* Update license year.

* Fix issue parsing Pylint output when there are no violations.

* Add support for Python 3.7 and 3.8
* Add support for [cfn-nag](https://github.com/stelligent/cfn_nag)
* Now using [ci.py](https://github.com/grantmcconnaughey/ci.py) for CI service detection

* Add support for GitHub Actions
* Add support for Drone CI
* Add support for Azure DevOps
* Add Windows compatibility

* Support for [cfn-lint](https://github.com/aws-cloudformation/cfn-python-lint)
* Support for overriding the default PR status context using `--context`
* Change: Default PR status contexts have changed from "Lintly" to "Lintly/{format}"