Support Node.js v0.12.x

[springmeyer]

Once Node.js v0.12.x is released we will add support, but until then only v0.10.x and older will be officially supported.
So, we are not planning to support > v0.11.3 < v0.12.0 as during this period node.js core has upgraded to v8 versions with major API changes. We will consider supporting these API changes once v0.12.0 is released and not before because keeping up will be a lot of work and a moving target.

[springmeyer]

closing, going to try to support v0.11 through NAN and the pull at #184