function Event() {
    var handlers = [];

    /***
     * Adds an event handler to be called when the event is fired.
     * <p>Event handler will receive two arguments - an <code>EventData</code> and the <code>data</code>
     * object the event was fired with.<p>
     * @method subscribe
     * @param fn {Function} Event handler.
     */
    this.subscribe = function (fn) {
      handlers.push(fn);
    };

    /***
     * Removes an event handler added with <code>subscribe(fn)</code>.
     * @method unsubscribe
     * @param fn {Function} Event handler to be removed.
     */
    this.unsubscribe = function (fn) {
      for (var i = handlers.length - 1; i >= 0; i--) {
        if (handlers[i] === fn) {
          handlers.splice(i, 1);
        }
      }
    };

    /***
     * Fires an event notifying all subscribers.
     * @method notify
     * @param args {Object} Additional data object to be passed to all handlers.
     * @param e {EventData}
     *      Optional.
     *      An <code>EventData</code> object to be passed to all handlers.
     *      For DOM events, an existing W3C/jQuery event object can be passed in.
     * @param scope {Object}
     *      Optional.
     *      The scope ("this") within which the handler will be executed.
     *      If not specified, the scope will be set to the <code>Event</code> instance.
     */
    this.notify = function (args, e, scope) {
      e = e || new EventData();
      scope = scope || this;

      var returnValue;
      for (var i = 0; i < handlers.length && !(e.isPropagationStopped() || e.isImmediatePropagationStopped()); i++) {
        returnValue = handlers[i].call(scope, e, args);
      }

      return returnValue;
    };
  }
A simple publisher-subscriber implementation.
@class Event
@constructor