Better support for named containers

[fancyremarker]

This modifies container matching to look only at the container name for cases in which a :container_name is explicitly provided. The spec I added demonstrates the use case I'm trying to support: namely, deploying newer versions of a tagged image when they become available. Right now, if I pull an updated version of the busybox image, I can't redeploy an existing busybox-container with the latest image, because the image ID doesn't match.

In particular, I get the following error:

STDERR: 2014/05/20 20:52:48 Error: Conflict, The name busybox-container is already assigned to 89efe3432bad. You have to delete (or rename) that container to be able to assign busybox-container to a container again.

Does this change jibe with your idea of how container resources should be used?

The kitchen tests passed locally, with the one exception of the apt-get failure addressed in #155.

[jperville]

Thank you @fancyremarker, I had same issue as you and I'm happy to find your PR. Looking forward to seeing this merged.

[bflad]

Since I was so far behind in reviewing/merging PRs, looks like I completely borked up this one with merging #147 and #157. I'll try to manually merge your commits then fix them up for Serverspec after I take a look at the others.