Unittest refactor

### This pull request is currently sitting on top of changes that are already in another pull request here: https://github.com/GoodBoyDigital/pixi.js/pull/301

The changes not to review here are in fd88b55, as it may be removed if the other is merged. I don't intend both to be merged of course, still would like either the other to be merged, or feedback for why not. If this one is merged in its entirety, then just close the other pull request.

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Why did I make a pull request of this now? Well because I think it's ready for a look through at this point. You can check out this branch, and run `grunt travis` or `npm test` to see the tests run.

I have put one functional test in as an example, though only the canvas renderer works for functional tests right now as there is no real feasible way **right now** to get WebGL to run in an X buffer session. That single test uses the auto-detector, so it should fall back to the canvas renderer and pass.

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As for the rest of this, all the unit tests are simply boilerplate, are in mocha, and pass in Firefox in Travis CI. That's really the point of making a pull request now; get a flow in place to run unit tests on each pull request with Travis.

*Functional tests can happen later that are Canvas 2d specific, and WebGL functional tests later than that, but unit tests will come shortly after this of course.*