Provides the base class for Plugins, which can be added to a PluginHost. 

3.1.1

No changes

3.1.0

* Added separate host method and host event specific subscription methods,
  to resolve inconsistency when using doBefore/doAfter in cases where the 
  host supported both an event and a method of the same name. 

3.0.0

No changes

3.0.0 beta 1

* Moved Y.Plugin to Y.Plugin.Base

* Host/Owner object now available through public "host" attribute, 
  as opposed to protected _owner property (this.get("host"))

3.0.0PR2 - Initial release
