doc: fix process.stdout reference to console.log
doc: fix process.stdout reference to console.log

This commit changes the word introduction to the code block to be
explicitly correct, and changes the `d` variable to `msg` for clarity.

PR-URL: https://github.com/iojs/io.js/pull/964
Reviewed-By: Jeremiah Senkpiel <f1782d15e31ad502ea2c097c21cc235811d0cb7c@rocketmail.com>
Reviewed-By: Nicu Micleușanu <7ba6b26002a178c6e17098ff478119ed69b20e64@gmail.com>
Reviewed-By: Vladimir Kurchatkin <928b42f72c5e646aa3a9189e4abed6635a777305@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node