Remote nrepl and nrepl jump

If emacs and clojure are running on different host types, nrepl-jump on a function defined in a resouce will fail. (nrepl is implicitly connected to a remote host)

e.g. M-. used on `map` should open clojure-1.4.0.jar and jump to the definition of `map`, instead it opens an empty buffer.

This fix checks if the resource is available locally to emacs before opening it. If it isn't, the nrepl-jump will fail in the same way as previously. 

If both the local and the remote machines are used for clojure development, resources in ~/.m2 should be available on both platforms and a local load is safe to do, thereby avoiding network traffic.

I have made a simple setup here:
https://github.com/klang/repl-tests