Pick up remote repl port from .nrepl-port in Maven/boot projects

[adamwielowieyski]

boot.core will create an .nrepl-port file as part of the repl task; it would be very useful to be able to automatically pick that up in non-Lein projects as well as Leiningen projects.

https://github.com/tailrecursion/boot.core/blob/master/src/tailrecursion/boot/core/task/repl.clj#L25