As it turns out, the docker-compose Python module is
required, and docker-py doesn’t cut it.
Even more confusing, docker-compose Python module installs
the docker Python module, which conflicts with docker-py. To
avoid this, there are additional docs to call this out.
When docker-compose become the sole method for using
Docker directly, some of this was shifted around in ways that
are inconsistent with other elements.
This adjusts it so that:
* The inventory variable default is set like the others, and
is less confusing
* We no longer mention the Standalone Docker in inventory
* We format our INSTALL docs w/r/t this var
Jeff Byrnes