Architecture: use zipper!?!

[paulkoegel]

Problem: in an onClick callback, we need to decide whether a card is moveable - this depends on its children.
A card is not moveable, when one of its children is out of order.
A card is moveable when it has no children or all of them are in order.
Example: [jack-of-spades, 2-of-diamonds] - the 2 of diamonds i moveable b/c it's the last card in the column, the jack of spades, however, is not moveable. It would be moveable if a 10 of diamonds was its only child.

Idea: use a zipper as the app state (cf. https://groups.google.com/forum/#!topic/clojurescript/RY5kEfSTc6k), so we can easily traverse from a clicked card to its children with the help of zipper functions.