Add dockerized redis configuration

[jgmontoya]

Sidekiq uses redis which should be dockerized.

We need to add the configuration to the docker-compose.yml file and set the env vars to use the docker assigned port (like it's done with the DB here).

This PR might help guide the needed changes.

[LuisFros]

You can use this repo where ive done that @jgmontoya https://github.com/LuisFros/rails-dockerizado