Initial tests for ClientRouter.

- TODO: The layout and each yielded template should have the option to opt-in to
  the data context. That way, it doesn't re-render if it doesn't need to.
- @tmeasday, right now, the layout and all yielded templates will re-render any
  time the router's data context changes, unless there is NO data context or the
  data context stays the same.
- A more likely scenario is the data context changes, but the user doesn't want
  the layout to re-render, just the yielded templates which would re-render
  anyway.