tough-ssm 0.4.0

Implements AWS SSM as a key source for TUF signing keys
Documentation
# Changelog
All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [0.4.0] - 2020-09-17
### Changed
- Update `tough` dependency to 0.9.0.

## [0.3.0] - 2020-07-20
### Added
- Added CI build of `tough-ssm`.

### Changed
- Update `tough` dependency to 0.8.0.

## [0.2.0] - 2020-06-26
### Changed
- Update `tough` dependency to 0.7.0.

## [0.1.0] - 2020-06-11
### Added
- Everything!

[0.4.0]: https://github.com/awslabs/tough/compare/tough-ssm-v0.3.0...tough-ssm-v0.4.0
[0.3.0]: https://github.com/awslabs/tough/compare/tough-ssm-v0.2.0...tough-ssm-v0.3.0
[0.2.0]: https://github.com/awslabs/tough/compare/tough-ssm-v0.1.0...tough-ssm-v0.2.0
[0.1.0]: https://github.com/awslabs/tough/releases/tag/tough-ssm-v0.1.0