lib: use arrow functions instead of bind

use `arrow functions` instead of `bind(this)` in order to improve
performance through optimizations.

PR-URL: https://github.com/nodejs/node/pull/3622


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>