major refactor for express-yui@1.0.0

this version is not compatible with previous version of the plugin.

changes

• the plugin is now a class definition that can be extended easily.
• leverage Y.Template.register() and Y.Template.get(), available in yui@3.12.x.
• a compiled version of the template is provisioned under the bundle object for runtime on the server side.
• yui output format is now opt-in using the format configuration.
• example does not use express-yui anymore, instead it uses express-view.
• the handlebars component can be controlled from outside by providing a custom version of it when creating an instance of the plugin.