run browser tests on ci

[wenzowski]

This depends on #4 so merge that first.

The encrypted env var will start working as soon as this is merged, though travis will have to be enabled for the repo of course.

Backchannel 2014-2-28

9:39:35 PM nateps: doing cross browser testing should be a priority now that things are getting more stable in derby
9:40:21 PM nateps: you can probably write the tests in a way where they can be run in phantom or loaded as a normal html page

Took longer than I'd hoped to get this figured out, but here it is.

[wenzowski]

here's what it would look like https://travis-ci.org/wenzowski/saddle/builds/20442342

formatting suggestions welcome

[wenzowski]

concurrent builds on travis currently clobber each other travis-ci/travis-ci#1366

[ericyhwang]

We're now going to move the DOM-based tests to be runnable with JSDOM, and use GitHub Actions for CI, since Travis has had large open-source backlogs the past month:
#34