src: s/node/io.js/ in `iojs --help` message
src: s/node/io.js/ in `iojs --help` message

Fix up a node reference that was missed in commit daf9562d.

PR-URL: https://github.com/iojs/io.js/pull/538
Reviewed-By: Colin Ihrig <838f779c91673db29b8572ea3f54d191d3878ae2@gmail.com>

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