Fix typo lenth->length

bin/node-sass

@@ -315,7 +315,7 @@ function renderDir(options, emitter) {
       renderFile(subject, options, emitter);
     }, function(successful, arr) {
       var outputDir = path.join(process.cwd(), options.output);
-      emitter.emit('warn', util.format('Wrote %s CSS files to %s', arr.lenth, outputDir));
+      emitter.emit('warn', util.format('Wrote %s CSS files to %s', arr.length, outputDir));
       process.exit;
     });
   });