Add travis bot for react-native

Reviewed By: AaaChiuuu

Differential Revision: D5588729

fbshipit-source-id: 7d1a08696f7680efb16cdbdb0ba131414d099962

.travis.yml

@@ -46,3 +46,4 @@ notifications:
     on_pull_requests: false
     on_failure: change
     on_success: change
+  webhooks: https://code.facebook.com/travis/webhook/