upgrade to nan v2.0

[julianduque]

Upgrade to NAN v2.0 API

[julianduque]

Not sure why io.js v3.0.0 failed on travis, I was able to build it properly on my local install

[drewish]

Looking at nan's example code I don't see any v8 includes. I wonder if we can just remove:

 #include <v8.h>
 #include <node.h>
 #include <node_object_wrap.h>
 #include <node_version.h>

And let NaN handle it? Curious if that would do anything about those errors.

[julianduque]

@drewish still the same errors, weird I can't reproduce those locally

[drewish]

Yeah looks like master is broken too. I'm going to play around with travis and see if I can get it building. If I can't figure something out pretty quickly I'll stop screwing around with it and just finish reviewing this. It seems like the broken build is independent of this.

[drewish]

Okay yeah this all seems legit. I'll screw with Travis without bothering you ;)

Thanks for the contribution!