Add Ubuntu bionic support to datagov-deploy-redis

[adborden]

Part of #571

As an operator, I want the datagov-deploy-redis role in its own repository as its own versioned, vendored ansible role with its own CI tests so that I have a reusable ansible role that is automatically tested under CI against Ubuntu Trusty and Bionic and can be deployed to different environments based on configuration.

Acceptance criteria

• README exists that describes dependencies, ansible variables, and example playbook
• Role exists in its own repo
• Role is versioned by git tag
• molecule configured to run against trusty and bionic
• Role is under automated testing with molecule
• CI is configured to run automated tests
• master branch is protected, requires PR review and passing CI checks
• datagov-deploy requirements.yml is updated with the new role

[adborden]

This was done a while back.