Turn off sending Travis notifications to IRC
Turn off sending Travis notifications to IRC

IRC ends up getting notifications for tests for any fork of ponyc. By using
Slack which requires notification, we only get notifications from the main
ponyc repo that has access to decrypt to encrypted credentials.

[skip ci]

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