Make the cli work with all versions of docker

[ciera]

Many versions of linux come bundled with an old version of docker (<1.7) that is mutually incompatible with later versions. The feature in question is the results from docker inspect. Old versions had a Volumes that mapped string to string. New versions have a Mounts that is an array of objects.

We already have code that works for both of these, we just need to special case based on the docker version.

[ciera]

The change was made in D126.

[ciera]

According to this, the change was at docker 1.8. http://www.adelton.com/docs/docker/docker-inspect-volumes-mounts

Still trying to get more precise info so that we can actually determine which version we are using.

[ciera]

This implies that they changed it in 1.8.0.
https://github.com/docker/docker/blob/master/CHANGELOG.md#180-2015-08-11

[ciera]

Fix submitted; have not been able to verify it yet. Our travis build still fails on this. I think that fails not due to docker versions, but due to running docker-in-docker.