dockerfile: upgrade to `sameersbn/ubuntu:14.04.20150604`
dockerfile: upgrade to `sameersbn/ubuntu:14.04.20150604`

outcoldman/docker-gitlab-ci,adiferd/docker-gitlab-ci,adiferd/docker-gitlab-ci,youhong316/docker-gitlab-ci,sameersbn/docker-gitlab-ci,outcoldman/docker-gitlab-ci,sameersbn/docker-gitlab-ci,youhong316/docker-gitlab-ci,bboehmke/docker-gitlab-ci,bboehmke/docker-gitlab-ci