title: res.locals returned undefined
body: <p>I'm trying to set some <em>response-specific</em> variables, and I'm getting <code>undefined</code> for <code>res.locals</code> when I log it from within my middleware, but it returns the function just fine if I log it from within a route function.</p>
  
  <pre><code>// all environments
  app.set('port', process.env.PORT || 3000);
  app.set('views', path.join(__dirname, 'views'));
  app.set('view engine', 'jade');
  app.use(express.favicon());
  app.use(express.logger('dev'));
  app.use(express.json());
  app.use(express.urlencoded());
  app.use(express.methodOverride());
  app.use(function (res, req, next) {
    console.log("res.locals from app.use middleware: ", res.locals);
    // res.locals.boom = 'nice';
    // res.locals.zoom = 'yeah!';
    next();
  });
  app.use(app.router);
  app.use(require('stylus').middleware(path.join(__dirname, 'public')));
  app.use(express.static(path.join(__dirname, 'public')));
  </code></pre>
  
  <p>Any ideas?</p>