Change TravisCI notification pattern
Change TravisCI notification pattern

Only send notifications to Zulip on sucess if the previous build
failed. This should cut down on noise in the Zulip notification
stream.

cquinn/ponyc,cquinn/ponyc,kulibali/ponyc,dipinhora/ponyc,ponylang/ponyc,dipinhora/ponyc,kulibali/ponyc,sgebbie/ponyc,jemc/ponyc,jemc/ponyc,cquinn/ponyc,sgebbie/ponyc,jemc/ponyc,sgebbie/ponyc,dipinhora/ponyc,kulibali/ponyc,sgebbie/ponyc,sgebbie/ponyc,cquinn/ponyc,ponylang/ponyc,kulibali/ponyc,ponylang/ponyc