TIP: fix bizarre Docker problems

docker rm -fv $(docker ps -aq)

Sometimes testing produces strange Docker-related problems.  The above command kills all containers, including the stopped ones.  The "-v" also destroys each container's private storage volumes.  This is great because Docker likes to run differently different times you run it -- because it has local state.  Local state is evil!  Run the above command every now and then so Docker starts from a clean, state-less, state.

In Docker, stopping a container is different from killing it.  The former stops the running container/process, but leaves the private volume.  The latter zaps the volume.

Thanks Sam!