Write how to documentation and example code in readme

PIVOTAL_TRACKER_STORY_URL=https://www.pivotaltracker.com/story/show/81819746
PIVOTAL_TRACKER_STORY_TYPE=feature
PIVOTAL_TRACKER_STORY_ESTIMATE=1
PIVOTAL_TRACKER_STORY_OWNER=carlsaturnino
PIVOTAL_TRACKER_STORY_REQUESTER=kdecastro
PIVOTAL_TRACKER_STORY_LABELS=docker images, docker-register