* Use GitHub Actions only
This retires Travis, and starts upload screenshot diffs when integration
tests fail.
* Use screenshots that match CI font rendering
* Run tests on Node 12
We had a bug where `stop()` was undefined but it fell back to the function on window which was inplicitly in the global scope.
This should reduce that kind of thing.
* Try running screenshot tests on Travis
* Standardize domain in integration tests
* Allow images to not match that well
* Turn back on all other tests