Fix url giving wrong signature base if used with Express app.use()

[tinnou]

If using Express 4 app.use() to mount certain routes paths, the req.url will be rewritten to reflect the mounted path. This has the effect of creating a wrong base resulting in an invalid computed signature. I changed it to use req.originalUrl since it preserves the original path.

e.g:
if you use

app.use('/users', users)

and in your users module you have

   /\* GET user by Id. */
    router.get('/:id',
        passport.authenticate('consumer', { session: false }),
        function (req, res) {
            console.log("Authenticated!");
    });

The req.url will be set to http://domain/12345 whereas req.original will be http://domain/users/12345