Private, local (and app specific) modules

I have a Node.js app with following structure:

+
|-- app/
|   |-- config.js
|   |-- modules/     // MVC app modules/components.
|       |-- login/
|       |-- signup/
|-- lib/             // App specific modules/libraries.
|   |-- auth/
|   |-- storage/
|-- node_modules/    // 3rd party modules.
|   |-- express/
|   |-- hjs/
|-- public/
|-- app.js
|-- package.json

What are the options to require modules from lib/ inside - for example - the login module, but without having to specify the relative path?

// app/modules/login/index.js

var auth = require('../../../lib/auth'); // <-- I'd rather have require('auth')

module.exports = function(app) {    
    app.get('/', auth.ensureAuthenticated, function(req, res) {
        res.send('/');
    });    
};

I do not want to host modules in lib/ on Github and would like to keep the *node_modules* directory for 3rd party modules only.

Modular web applications with Node.js and Express (see 2:25) by TJ looks very promising when he talks about bundledDependencies. But that doesn't seem to work yet.

Update:
I've now flattened my structure a little and decided to embrace relative paths instead.