Adding basic support for popstate event

https://developer.mozilla.org/en-US/docs/Web/Events/popstate
It allows the navigation with the browser "back button".

This is a simple implementation and it works with major browsers + IE10+.

Also, it's good to send the you ID "state". If you have multiple libraries changing the state of the URL, you need to know if you are responsible for that route. That's why I am passing {edenjs: true} as a state.