add note about class bindings to changelog
add note about class bindings to changelog

NYTimes/backbone.stickit,Krasnyanskiy/backbone.stickit,adam-26/backbone.stickit,Krasnyanskiy/backbone.stickit,akre54/backbone.stickit,akre54/backbone.stickit,NYTimes/backbone.stickit,adam-26/backbone.stickit