Remove all AsyncListener JS code

Squashed for simplicity. There are also changes in the naming of some of the native API's so what it's called actually reflects what is going on. Also added a few TODO's, etc.

Review, comment, and if necessary I'll break up the commits into relevant segments.

Also, didn't add https://github.com/tjfontaine/node/commit/6a74d6c to the changes. If that conditional is hit then there's a bug in the code. I'd rather add an `ASSERT()` or the like that can be reported instead of silently ignored.

/cc @tjfontaine @indutny @orangemocha
@trevnorris I'm also wondering how users can use the request object in their callbacks. What's the use case? Could you show us an example? Also, I don't know how much we're concerned about breaking compatibility with 0.12, but how would this break 0.10.x code and is it an issue?