Allow for nrepl transport to be specified

nREPL supports a tty transport that allows for a user to telnet into nREPL
rather than having to use the default bencode protocol.

This is fairly useful with SublimeREPL as it doesn't have a 'connect to a
bencode repl' option, just a 'launch `lein repl` and 'telnet to a repl' options
for Clojure.