Travis CI integration is broken post move from travis-ci.org to travis-ci.com

[andrewmains12]

travis-ci is a company now; we need to migrate from travis-ci.org to travis-ci.com. See https://docs.travis-ci.com/user/migrate/open-source-repository-migration .

To figure out:

• Are the builds free?

Should we be moving somewhere else? https://www.jeffgeerling.com/blog/2020/travis-cis-new-pricing-plan-threw-wrench-my-open-source-works suggests we don't get free builds anymore, so the answer is probably yes.