Update Slack notification for Travis builds (#9134)
Update Slack notification for Travis builds (#9134)

The main purpose is to get notifications for cron builds since they
currently failing without any notification.
benmccann/playframework,benmccann/playframework,mkurz/playframework,playframework/playframework,wegtam/playframework,marcospereira/playframework,marcospereira/playframework,playframework/playframework,mkurz/playframework,wegtam/playframework,marcospereira/playframework,marcospereira/playframework,wegtam/playframework,wegtam/playframework,mkurz/playframework,mkurz/playframework,benmccann/playframework,playframework/playframework,benmccann/playframework