Deprecate domains

ref https://github.com/iojs/io.js/issues/66

Also, I did notice that `domain.dispose()` is deprecated but missing a deprecation message. So it includes a commit which fixes it. Please inform me if you want it as a separate pull request.

I've also changed two test assertions. I belive usage of domain in `lib/repl.js` was swallowing the assert errors and that those are currently broken.
Sure, but shouldn't that be guaranteed by the api that the exit code is only fired once? If not, there probably a lot of broken code out there.