/*
Adds items asynchronous to the list, good for adding huge amount of
data. Defaults to add 100 items a time
function(values, callback, items) {
        var valuesToAdd = values.splice(0, 100);
        items = items || [];
        items = items.concat(self.add(valuesToAdd));
        if (values.length > 0) {
            setTimeout(function() {
                addAsync(values, callback, items);
            }, 10);
        } else {
            self.update();
            callback(items);
        }
    }