fs: deprecate fs.read's string interface

`fs.read` supports a deprecated string interface version, which is
not documented. It was intended to be deprecated in this commit in 2010
https://github.com/nodejs/node/commit/c93e0aaf062081db3ec40ac45b3e2c979d5759d6
This patch issues a deprecation message saying the usage of this
interface is deprecated.

PR-URL: https://github.com/nodejs/node/pull/4525


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>