Add example of navigation testing

[DavidFrahm]

I would love to see this repo cover a scenario where you navigate across pages. Ideally covering navigation handled two ways: one via a simple stencil route link, and another via a button which calls a function to programatically navigate.

For example:

1. Load the root url: "/"
2. Find a navigation link: <stencil-route-link url='/page-2' ...
3. Click the link
4. Assert page is Page 2
5. Find a navigation button <button onClick={() => this.gotoPage3()} ...
6. Click the button
7. Assert page is Page 3