Core.clj: moved serve-new-cards further back since
it relies on unmark-all-cards now.
Core.cljs: pass channel to card-views inside piles-view as well.
moveable?: pass in column-cards - function doesn't need to know about the entire column.
test.cljs: fixed.
core.cljs: serve new cards when enter is pressed.
column-view: added column-placeholder-view which gets rendered when there are no more cards in that column.
core.cljs: added index-for, pile-for, path-vector-for-card.
We can undo stuff ^_^