Setup multi-environment testing

[chrisdpeters]

• Integrate with appraisal or gemika gem
• Add simple Docker + RVM config for testing different Ruby versions and DBs locally

[jmfederico]

• Integrate with appraisal or gemika gem
• Add simple Docker + RVM config for testing different Ruby versions and DBs locally

[chriscz]

@jmfederico Can look at using passenger-docker for this. I have a partially working docker file which does a capistrano deployment internally so not exactly matching your use-case, but the basics are there. See https://github.com/chriscz/capistrano-puma-test-app/blob/main/Dockerfile