Update Docs for Docker Compose New Install Method

[jvanderaa]

The new instructions for Docker Compose puts compose as an option of the Docker executable. These docs should be updated to reflect this.

[itheodoridis]

I believe this is dependent on the docker compose version, not on docker executable directly. So the version should be mentioned but perhaps also a link to an installation how-to for docker compose. The Digital Ocean guides are great for this, or maybe one should be written from scratch or adapted.

[jdrew82]

This has been corrected so closing.