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 <cjihrig@gmail.com>

src/node.cc

@@ -2874,7 +2874,7 @@ static void PrintHelp() {
          "       iojs debug script.js [arguments] \n"
          "\n"
          "Options:\n"
-         "  -v, --version        print node's version\n"
+         "  -v, --version        print io.js version\n"
          "  -e, --eval script    evaluate script\n"
          "  -p, --print          evaluate script and print result\n"
          "  -i, --interactive    always enter the REPL even if stdin\n"