Refactor & add tests for last-word fetch
Bump nREPL for stdin fix
Add tests actually exercising the completer
Add integration test

- Exercise nREPL / initialization features, the area of the most common
  breakages.
- Convey *out*/*err* bindings to the nREPL print-handling thread. Good
  for testing, but also just a good idea all around.
- Pass input-stream/output-stream the whole way down through the
  ConsoleReader (bugfix)