Test original twentyfourteen navigation logic

The navigation in this script happens through `window.location` assignment, not a method call, which we can't spy on with Sinon. In order to verify that this script is working correctly from the tests, we have two options:

1. either refactor to expose the navigation logic as something we can stub out (the easier approach, which we took here), or else
2. refactor the script so that `window` is passed in by reference, allowing us to pass a mock object instead for a sort of light-weight dependency injection.

The latter approach is better-suited to situations where your entire application is built modularly, e.g. with [RequireJS](http://requirejs.org/); in fact, the [Squire.js](https://github.com/iammerrick/Squire.js/) library exists specifically to enable dependency injection for Require modules, and the [AngularJS](http://angularjs.org/) framework is designed from the ground up to enable idiomatic dependency injection.