Create image version tags

[pieterlange]

I think it makes sense to use the version of the awscli package itself (eg quay.io/coreos/awscli:1.11.167). Maybe include an additional coreos version tag as is done with the hyperkube image.

[whereisaaron]

Oh you already said the same thing I added to #16 @pieterlange, I'm five days late to the party 😄

When an image it promoted/release to 'latest', can it also be tagged with a version? With version tags, users can pull version tagged images that won't be subject to potentially breaking changes like #15.

I suggest tagging them with the version of awscli they contain, since this the only purpose of the container. But really, any version tag to maintain an invariant image would be enormously helpful.