Make the e2e tests easy to run
It should be possible to anyone with docker to be able to run something like
# Make some biboumi changes make check docker run --name biboumi-charybdis -P docker.louiz.org/louiz/biboumi/charybdis make e2e
We just need to
- make a public charybdis image that can be used by contributors, AND in our gitlab-ci tests.
- document how things work
And this would let us remove many dependencies from our internal gitlab-ci images, to make them lighter.