Fix printing of stdout/err, drop (vestigial?) nrepl-eval fn

AFAICT, the `nrepl-eval` fn is not necessary.  Perhaps there was an issue with piggieback ~0.0.2 that prompted it?

Anyway, bumped piggieback to 0.0.4, eliminated `nrepl-eval`, and all's well.

Thanks for the sane REPL environment! :-)