NotificationWidget = function (selector) {
        this.selector = selector;
        this.timeout = null;
        this.busy = false;
        if (this.selector !== undefined) {
            this.element = $(selector);
            this.style();
        }
        this.element.hide();
        this.inner = $('<span/>');
        this.element.append(this.inner);
    }
Construct a NotificationWidget object.

@constructor
@param {string} selector - a jQuery selector string for the
notification widget element