doc: minor clarification in the modules API doc.
doc: minor clarification in the modules API doc.

PR-URL: https://github.com/nodejs/io.js/pull/1983
Reviewed-By: Jeremiah Senkpiel <f1782d15e31ad502ea2c097c21cc235811d0cb7c@rocketmail.com>
Reviewed-By: Ben Noordhuis <59bd0a3ff43b32849b319e645d4798d8a5d1e889@bnoordhuis.nl>

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