Type definitions for express 3.1

I created the definitions to express 3.1 and added documentation comments to facilitate the Visual Studio intellisense. To use this definition:

	/// <reference path="express-3.1.d.ts" />

    var express = <Express>require('express');
    var app = express();
	
	...
	
	app.get('/example', function (req, res, next) {
		res.send(foo);
	});
	
	...