Don't rely on ev.state to detirmine initial load

Add a simple bool the prevents popState from affecting dispatching until
the first dispatch is called.

This should fix the issue where the initially entered page could be navigated back to using the back/forward buttons.

![](http://cdn4.list25.com/wp-content/uploads/2011/11/aboss.gif)

@barnabyc @flahertyb