Added @deprecated tags to menunav and focusmanager

As voted on in [this yui-contrib thread](https://groups.google.com/forum/?fromgroups=#!topic/yui-contrib/I28zUGYPBoA), `node-menunav` and `node-focusmanager` are now deprecated.

Reviewers, please let me know if there are any additional steps required to officially deprecate a component.