Starts the show animation whenever init has completed.
function _startShowAnimation(item, spec) {
        if (!item.halted) {
            var callback = item.showCallback;
            if (spec.transform) {
                item.mod.setTransform(Transform.identity, item.options.show.transition, callback);
                callback = undefined;
            }
            if (spec.opacity !== undefined) {
                item.mod.setOpacity(1, item.options.show.transition, callback);
                callback = undefined;
            }
            _startTransferableAnimations.call(this, item, callback);
        }
    }