Revert "stream: add bytesRead property for readable"

This reverts commit bfb2cd0b.

The bytesRead property, as implemented, tracks characters
instead of bytes when using an identity encoding.

Refs: https://github.com/nodejs/node/pull/4372
PR-URL: https://github.com/nodejs/node/pull/4746


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>