Update to compile under 0.10

It looks like both #46 and #47 are related to getting a working compile under node >=0.9.4. This PR fixes that problem by doing several things:

1. Uses the casting trick [recommended in the wiki](https://github.com/joyent/node/wiki/Api-changes-between-v0.8-and-v0.10). While it's aesthetically preferable to just add the status parameters to the `After*` callbacks, this would break the compile under 0.8, and we're not using the status anyway.
1. Adds a `NODE_MODULE` declaration
1. Updates `segfault-handler` to the tip of master, which can compile under v0.10.

I've tested this on my machine under v0.8.8 and v0.10.7.