YUI Custom Events
    Custom event system

3.4.0
    - Custom events published from Y no longer bubble by default.


3.3.0
    - Undocumented and poorly named 'each' method on EventHandle changed to 'batch'.
    - After listeners for events fired in a defaultFn or listener are queued in the correct order.
    - Added Y.Do.originalRetVal and Y.Do.currentRetVal statics accessible by Y.Do.after subscribers.
    - Exposed the previously private EventTarget.parseType

3.2.0
    - Fixed defaultTargetOnly publish configuration
    - Detach now decrements subCount/afterCount
    - Detaching via category no longer affects subscriptions on other objects

3.1.1
    - No changes

3.1.0
    - Wildcard prefix subscriptions supported:
      target.on('*:click', ... will be notified when 'tree:click',
      'tab:click', etc are fired.
    - Added EventTarget::once, which is equivalent to on(), except the listener
      automatically detaches itself once executed.
    - Added event monitoring.  When configured, an event target will
      emit events for publish, attach, fire, and detach operations on
      the hosted events.
    - EventTarget::on's type parameter is overloaded to accept arrays and objects
      for attaching multiple types at once.
    - EventTarget::detach returns the event target like the API docs
      already stated.
    - Events can now be configured to execute the defaultFn only on the
      targeted object, not on the bubble targets.
    - The event order has been reworked so that the after listeners
      for the entire event stack execute after all defaultFn across
      the entire bubble stack.

3.0.0
    - Broken into core base and complex modules.
    - broadcast works for simple events.
    - If configured to return an event handle, the return value
      will always be a single object, regardless of how many listeners
      were attached.  Previously, multiple listeners provided an array
      of detach handles.

3.0.0beta1
    - Implemented the broadcast flag.  broadcast = 1: local, accessible
      via Y.on('prefix:event'). broadcast = 2: global, accessible
      via Y.on or globally via Y.Global.on('prefix:event).  Broadcast
      listeners cannot effect the defaultFn or host subscribers (so
      are in effect, after listeners), although this is still possible
      by added either Y or Y.Global as event targets.
    - Moved custom event out of event package
    - EventTarget accepts a prefix configuration.  This is used
      in all exposed methods to handle shortcuts to event names,
      e.g., 'click' and 'menu:click' are the same if the prefix
      is 'menu'
    - Exposed methods are 'on' for the before moment, 'after' for
      the after moment, and 'detach' for unsubscribe.  subscribe,
      before, unsubscribe, and corresponding methods are deprecated.
    - Event type accepts a event category which can be used to
      detach events.
      Y.on('category|prefix:event', fn);
      Y.detach('category|prefix:event');
      Y.detach('category|*');
    - Added 'chain' config to events that makes the return value the
      event target rather than a detach handle.  Use with the detach
      category prefix.
    - The type parameter can be an object containing multiple events to attach
      Y.on( { 'event1': fn1, 'event2': fn2 }
    - Y.fire payload for event facades can be another facade or a custom event.