Use Chrome for CI tests

[BrianSipple]

From what I've been able to gather, the test failures in #28 all seem to be due to PhantomJS not supporting either Array.find or HTMLElement.remove().

All tests pass in Chrome.

With that in mind, now might be a great opportunity to set up Chrome for CI tests -- especially given how much we're doing with the DOM. All we need is a few travis.yml and testem tweaks, and we'd be all set.

[nathanhammond]

I'm actually opposed to this since every Ember app is set up to use Phantom by default. It'd be really easy for us to accidentally introduce a feature that didn't work on Phantom once we move CI to Chrome. I'd much rather ship a polyfill for this behavior in our tests so that we don't accidentally introduce regressions–especially since our code is designed to be run at test time.

[BrianSipple]

@nathanhammond Good point, I hadn't yet wrapped my brain around the fact that we're designing for use in tests here as well. I'll close the issue -- I think those concerns far outweigh the benefits atm -- but hey, it's good to know now that this challenge might come up!.