Created by: cvrebert
I still need to muck around with Savage a bit for this, but the idea is that for Sass or JS PRs, Travis can build the docs with the PR's changes and upload a copy to http://preview.twbsapps.com/c/${commit-sha}/ (and eventually we can post a GitHub comment that links to the URL). This is more convenient than having to pull down the PR locally, run Grunt, and then run Jekyll. Also, we can eventually point Sauce/BrowserStack/etc. at these public URLs, instead of setting up a local tunnel to Travis, which can be flaky/slow sometimes.
CC: @twbs/team