eio_custom -> uv_queue_work

I'm just tired of seeing:

    WARNING: ev_ref is deprecated, use uv_ref
    WARNING: ev_unref is deprecated, use uv_unref

References:
https://github.com/joyent/node/wiki/How-to-migrate-from-eio_custom-to-uv_queue_work
https://gist.github.com/TooTallNate/1368935