Update for changes in Travis CI's webhook payload format.

Review Request #10970 — Created March 26, 2020 and submitted — Latest diff uploaded

Information

rbintegrations
release-1.0.x
9ab860b...

Reviewers

Travis CI has made some changes to their webhook payload. These are
currently effective on travis-ci.com, and will likely be making it to
travis-ci.org soon.

The biggest of these is that the global_env key is completely gone.
There's a top-level env key, but that's in a weird hard-to-parse
format. I've changed it to pull the relevant keys out of the matrix data
instead.

Second, I was encountering a new errored state for some builds. I've
added handling for this and logging for any future states which we don't
handle.

Posted some changes that triggered Travis CI builds and saw the webhook
handler work correctly.