Tag student released version

[psychemedia]

The tagging strategy is not great if we need to keep containers around for particular presentations; docker images are tagged with hashes but it would also be useful to be able to tag things:

• with a presentation code;
• with a current tag for the (latest) current image.

There is also a build datetimestamp inside the container for keeping track of images. (I wonder if there's a way of getting the Github hash in there as well?)

The following manual command should pull the latest image built from a release of this repo at ousefuldemos/tm351-binderised:latest and tag and push it as a "release" container on another Dockerhub organisation: ousefulcoursecontainers/ou-tm351:current

docker pull ousefuldemos/tm351-binderised:latest && docker image tag ousefuldemos/tm351-binderised:latest ousefulcoursecontainers/ou-tm351:current && docker push ousefulcoursecontainers/ou-tm351:current