old_contents: var app = require('./server/app');
  app(__dirname).listen(3000);
  console.log('listening on port 3000');
  
new_contents: var server = require('./server/app')(__dirname);
  server.listen(3000, function() {
    console.log('listening on port 3000 in', server.env);
  });
  
subject: update server.js