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.
Actually, how it is implemented now makes the REPL catch all uncaught exceptions. Maybe that should be possible to change with an option and be disabled by default if you are using the REPL as a library.

I think this is getting out of scope for this pull request. Maybe it should be addressed in its own? But it needs to be addressed before the deprecation can be merged.