Supporting node 0.11 using Nan

I have started working on a music app recently and wanted to use node 0.11 (I'm using Koa). So I've ported the bindings to use [Nan](https://github.com/rvagg/nan).

Tests pass on node 0.10 and 0.11, on Ubuntu. I haven't tried on OSX or Windows.

I'm not sure if this would have been better based off another branch? Anyway, let me know and I can make and changes necessary.