update to latest ubuntu 12.04.3
add docker gpg key to avoid package warning
add docker group
add virtualbox builder
update kernel only on aws, as 12.04.3 has 3.8.0-29
enable memory and swap cgroup
Merge pull request #4 from justone/docker-inst-updates

Docker inst updates
Merge pull request #3 from justone/add-vbox-and-latest-ubuntu

Add vbox and latest ubuntu
Don't run scripts/vagrant.sh on Amazon
Update to the latest 12.04 EBS AMI
Run the amazon scripts with root
DOn't run vm_cleanup.sh for Amazon
add the ubuntu user to the docker group too