Support for hot reload

First of all: Bide just works! It's great. Thank you!

I'm using shadow-cljs and that means frequent reloads of code.
However, I have to stuck any bide setup code in init (i.e. it only runs once), since it seems there's no `stop!` method and setting up another router leads to multiple registration of navigation events (i.e. after 4 re-loads any click on a route is done 4 times).

Would be great to have a `stop!` function to cleanup or a way to dynamically add routes.