Allow third value 'tidy for cider-macroexpansion-suppress-namespaces.

This is the elisp part of the cider-nrepl feature pull request https://github.com/clojure-emacs/cider-nrepl/pull/100.

I've chosen `tidy` as third value, because it does even more than just printing alias/var for vars from aliased namespaces.  It also handles refered vars and vars in the current namespace.