Create systemd unit file

PIVOTAL_TRACKER_STORY_URL=https://www.pivotaltracker.com/story/show/81819750
PIVOTAL_TRACKER_STORY_TYPE=feature
PIVOTAL_TRACKER_STORY_ESTIMATE=2
PIVOTAL_TRACKER_STORY_OWNER=carlsaturnino
PIVOTAL_TRACKER_STORY_REQUESTER=kdecastro
PIVOTAL_TRACKER_STORY_LABELS=docker images, docker-register
@joshuarubin What should be the format of the etcd keys?