Tianon made a micro-image (sub one meg?) that we can use as a very fast to download 'yes, your docker can download and run an image' test

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #7027 from SvenDowideit/use-a-hello-world-micro-image

Tianon made a micro-image (sub one meg?) that we can use as a very fast ...