use docker 1.6 in circleci
use docker 1.6 in circleci

see https://forums.docker.com/t/fata-0001-error-status-400-trying-to-push-repository-username-reponame-mycustomtag-access-denied-is-a-private-image/1354/12

hackedu/website,zachlatta/website,zachlatta/website,zachlatta/website,hackedu/website,hackedu/website