README: show TravisCI build status for devel branch
README: show TravisCI build status for devel branch

william-p/phantomas,ingoclaro/phantomas,gmetais/phantomas,gmetais/phantomas,ingoclaro/phantomas,william-p/phantomas,william-p/phantomas,gmetais/phantomas,macbre/phantomas,macbre/phantomas,ingoclaro/phantomas,macbre/phantomas