Explicate the version of Docker (lxc-docker package)
Give non-root access

ref.
  http://askubuntu.com/questions/477551/how-can-i-use-docker-without-sudo
  http://docs.docker.com/installation/ubuntulinux/#giving-non-root-access
  http://qiita.com/itiut@github/items/85a473059fceab7f7159
Merge branch 'docker'