Adds an event that fires when a route has completed.

This creates a clean single-fire event over simply watching for a `routeChange` event to watch for completed route changes.
Since we're checking whether the new controller calls a redirect, I think it might need to be something like:

```
currentPath = parentController.path
@createController element: container, parent: parentController, name: name
if parentController.path is path # if no redirect was called
  @trigger 'routeComplete'
```

Except I'm not sure if that will work, because it might be asynchronous, the routing. We might need to add a flag/property in the controller redirect call.