File metadata terminus in pure clojure

This implements a compojure app to compute file metadata in pure clojure instead
of resorting to the jruby puppet service.

This doesn't yet support file_metadatas nor the special "plugins" and "modules" mount.
This also doesn't cache the found metadata yet.

Signed-off-by: Brice Figureau <brice@daysofwonder.com>