Specify required version of docker compose in the README

[bhpayne]

Specify the version in documentation and see if we can check the version in the script

[bhpayne]

On my laptop I'm running

$ docker-compose version
docker-compose version 1.29.2, build 5becea4c
docker-py version: 5.0.0
CPython version: 3.9.0
OpenSSL version: OpenSSL 1.1.1h  22 Sep 2020

[bhpayne]

As per https://docs.docker.com/compose/compose-file/compose-versioning/ there are three versions to track:

• docker-compose, which is 1.29.2 on my laptop
• Compose file format, which is 3.6 in both https://github.com/allofphysicsgraph/proofofconcept/blob/gh-pages/v7_pickle_web_interface/docker-compose.yaml and https://github.com/allofphysicsgraph/proofofconcept/blob/gh-pages/property_graph/docker-compose.yaml
• Docker Engine release

$ docker --version
Docker version 20.10.11, build dea9396

[bhpayne]

done