Added function to get current state.

[akoppela]

I've did Elm format and added function to get current state. Added tests for functions to work with State as well.

This library keeps a track of selections by key and mouse private. But sometimes it's nice to have access to them. E.g. when I want point to correct aria-activedescendant. Yes it's possible to store local copy, but that does not make sense to do that, because they are already stored. So to store local copy could create potential impossible states.