Circle CI + Rails Config

1. inside Circle CI > your organization, click "New Project" then 'start build' to save it (build will fail)
2. navigate to project Environment Variables (eg: https://ui.circleci.com/settings/project/github/your_username/your_repo/environment-variables)
3. click 'Add Variables' and add the following: HEROKU_APP_NAME, HEROKU_API_KEY
4. HEROKU_APP_NAME is whatever found inside app-name-here.herokuapp.com
5. HEROKU_API_KEY may be created via $ heroku authorizations:create --description='App Name' (copy/paste the 'token' value)
6. add this repo's config.yml inside your Rails project: .circleci/config.yml
7. update Ruby version within the "Docker image", e.g. 2.6.1, inside your config.yml
8. $ git push to build the project on Circle CI
9. if tests pass, project will be deployed automatically to Heroku