3.0.0 beta 1

* Removed Attribute.CLONE support in the interests of simplicity.
  Was not being used. Can re-evaluate support if real world demand 
  for it exists. 

* Changed "set" and "get" configuration properties for setter and 
  getter methods to "setter" and "getter" respectively.

* Added support for setter to return Attribute.INVALID_VALUE
  to prevent attribute state from being changed. 

  This allows developers to combine setter and validator 
  functionality into one method if performance optimization 
  is required.

* "validator" is now invoked before "setter".

* Renamed xxxAtt and xxxAtts methods to xxxAttr, xxxAttrs for
  consistency.

* "after" listeners are only notified if attribute value really
  changes (preVal !== newVal).

* Extending classes can now overwrite ATTRS configuration properties 
  from super classes, including writeOnce and readOnly attributes.

  The ATTRS configurations are merged across the class hierarchy,
  before they are used to initialize the attributes.

* addAttr now prevents re-adding attributes which are already 
  configured in order to maintain consistent state.

* Event prefix wrapper functions (on, after etc.) removed - 
  Event.Target now accepts an event prefix configuration value
  
* Added additional log messages to assist with debugging.

* Attribute change events are no longer fired for initial set.

* Split up State add/get/remove into add/addAll, get/getAll, 
  remove/removeAll to avoid having to create object literals for 
  critical path [ add/get single key values ].

* Attribute getter, setter, validator now also receive attribute name 
  as the 2nd arg (val, name).

* If Attributes initialized through addAttrs have a user provided value 
  which is not valid, the initial attribute value will revert to the 
  default value in the attribute configuration, if it exists.

* reset() no longer resets readOnly or writeOnce attributes. Only 
  publically settable values are reset.

* Added modifyAttr method, to allow component developer to modify 
  configuration of an attribute which has already been added. The set of 
  attribute configuration properties which can be modified after it 
  has been added are limited to getter, readOnly, writeOnce and broadcast.

* Added support for lazy attribute configuration. Base uses this feature 
  to lazily intialize all Attributes on the first call to get/set, for 
  performance optimization. 

  lazyAdd:true/false can be used to over-ride this behavior for a 
  particular attribute. 

3.0.0PR2

* Added valueFn support, to allowing static 
  attribute values configuration to set instance
  based values.
  
* Added reset method.

* Added private setter for use by class implementation
  code to set readOnly, writeOnce values.

3.0.0PR1 - Initial release

Module Name: "attribute"
Documentation: http://developer.yahoo.com/yui/3/attribute

The Attribute utility allows you to add attributes to any class 
through an augmentable Attribute interface. The interface adds 
get and set methods to your class for attribute access, in 
addition to supporting change events allowing you to listen 
for changes in attribute values.