update for node v0.11.13

hey bro... this updates to the latest nan version for node v0.11.13 support (the api that will basically be 0.12).

some things:
1. the index property code is duplicated/added - instead of just casting it to a string... locally I'm doing some tests with dynamic arrays. I'll try and commit some tests soon.
2. converted a few more things to symbols. we'll make macros soon.

cheers!