Personally, what I _started_ doing with the refactor was only put global assumptions into the file. In other words, I had no browsers specified by default and expected you to pass them locally (or during travis).

I'm not even sure which of the two cases we should hard-code into the file. It makes sense to put the most common browser into the file that you test with locally (chrome?), or maybe it's best to do the travis browsers since those are fixed and you're just going to override our assumptions locally anyway?