Test docker images before pushing them

[martinthomson]

This might require some tweaking, but it might be worth some automated testing of docker images before pushing them. Right now, that might just mean running the behave tests. Not sure about the archive scripts though, which were the cause of recent issues; those are not directly tested.

[MikeBishop]

There are behave tests for the archive script in the archive repo. Maybe this is the time to switch over to pulling the archive tool from its own repo? Then you would just need some wiring to run those tests in your Docker container.

[martinthomson]

Maybe I can look at https://github.com/MikeBishop/archive-repo/issues/2 and just go from there. At that point, I don't need to worry about getting the dependencies right. I do have testing that uses the core docker image, it's just that those tests run after any bugs hit production code, which is not ideal.