Example with Docker Compose

[vovimayhem]

I added a docker compose example file to quickly launch the example with Docker Compose.

Example usage:

# Move to the directory:
cd actioncable-examples

# FIRST TIME ONLY: Run the setup script inside a temporary app container:
docker-compose run --no-deps --rm web setup

# Launch the redis, web & cable containers - will download & launch a working redis container automatically:
docker-compose up

Merge to master in case you guys are interested on it :) Cheers!