Use clojure.walk/macroexpand for macroexpand-all
Removes ritz-javadoc support that migrated into nrepl

Javadoc support moved into nrepl core, so supporting javadoc in ritz
is no longer necessary.

Fixes pallet/ritz#71
Use lein 2 plugin loading for hooks

Removes the need to add explicit hooks.
Update to nrepl.el 1.6