Get tests running on travis

[DanTup]

(This isn't ready yet, I'm just opening a PR for convenient running of it without setting up Travis on my fork :-))

[DanTup]

Ok, I've got the tests running on macOS on Travis (both the integration test and the browser-based tables test). The previous Travis config was just running on Linux (the default if not specified) so this changes to OSX.

On Linux, the tables test now passes (we have to run in --no-sandbox mode) but the integration test fails to connect. I may need to set up a VM or Docker locally to try and repro that here to debug better - I'm not sure how much time we want to spend on setting this up on other platforms (on one hand, it's a web app so hopefully platform doesn't matter much, but on the other hand we've had more issues on Windows than we'd like so covering them all might not be a bad idea).