Add dpxdt screenshot diffs to cycledash

Things to note:

- I created a new environment var, `ALLOW_LOCAL_VCFS`, which does what you'd expect.
- I include the [official React ES5 shims](http://facebook.github.io/react/docs/working-with-the-browser.html#browser-support-and-polyfills) in the prod build.
- Simulating click events wasn't as straightforward as I'd hoped. React ignores jQuery's `.click()`. I wound up using a [deprecated API](https://developer.mozilla.org/en-US/docs/Web/API/document.createEvent) because Phantom needed it.

It should be pretty straightforward to add new screenshot diffs. We should even be able to screenshot diff BioDalliance!
Should this be included?