Upgrade to [email protected] - refs #125

[springmeyer]

This starts using Nan::AsyncResource (aka Node::AsyncResource under the hood) to enable us to upgrade to latest nan without hitting deprecation warnings (that we turn into errors in skel due to our use of -Werror).

What is Node::AsyncResource?

It looks like it is a simple C++ class that needs to be created and passed to all callbacks. It looks like it is needed to be able to support this JS-land API: https://nodejs.org/api/async_hooks.html

My understanding is that we need to create one with a unique name. The Nan wrappers make this easy: https://github.com/nodejs/nan/blob/master/doc/asyncworker.md#nanasyncworker.

For the one place what we call a callback directly (not using Nan) this PR creates a Nan::AsyncResource directly.

refs mapbox/mapbox-gl-native#11288
refs #125

[springmeyer]

Summary is that one should use Nan::Call for sync calls, and Nan::Callback::Call for async.

from sass/node-sass#2298 is relevant since we do both sync and async calls.