Fix extrusions

[MattFerraro]

The main issue as far as I can tell is that when you do this:

currentlySelected.subscribe(store, {
    console.log($currentlySelected)
})

You only have access to the old value of $currentlySelected. To get the latest you have to use:

currentlySelected.subscribe(store, {
    console.log(store)
})

This fixes #71