Add cpuset option to kitchen docker

This adds the cpuset option to allow providing affinities to suite containers.

I also added a mechanism to check the current docker version, as the cpuset feature is only available after 1.1.0. If you specify the option but have an older docker version installed then a UserError is thrown. I felt the best way to deal with this was to fail early and let the user know if they want to use this option then upgrade docker.