disable Travis notification config
disable Travis notification config

I added this back when rust-ci.org was still up, because it would keep sending
"it is fixed" messages after fixing a build. The fixed build would be
re-triggered every day until something new was pushed. Now that Rust CI has
stopped working, it serves no purpose any more. Simpler is better.

ruuda/claxon,ruuda/claxon,ruuda/claxon