FEATURE REQUEST: pass next() in precondition to decide whether the router should *change* the current route

[sallliisa]

The current model of the router is regardless of the route passed the pre-condition of each of the route, the actual route still changes. It would be nice and much more coherent i think if I could decide whether to go to the next route or not based off of the precondition that I defined.

[ItalyPaleAle]

This can't really be stopped because the navigation happens in the browser. The router can only react to that.

More discussion here: #112