PHP Project Composer autoload can't find the classes - class

Question

I'm building an authentication system and I use Composer to manage dependencies.
When I run my project it seems none of the classes can be found. I generated the files using cmd. I found similar threads here and here but it does not quite do it... Any idea?
The error
Fatal error: Class 'Bixxcom\User\User' not found in
C:\xampp\htdocs\authentication\app\start.php on line 34
start.php
<?php
use Slim\Slim;
use Slim\Views\Twig;
use Slim\Views\TwigExtension;
use Noodlehaus\Config;
use Bixxcom\User\User;
use Bixxcom\Helpers\Hash;
session_cache_limiter(false);
session_start();
ini_set('display_errors', 'On');
define('INC_ROOT', dirname(__DIR__));
require INC_ROOT . '/vendor/autoload.php';
$app = new Slim([
'mode' => file_get_contents(INC_ROOT . '/mode.php'),
'view' => new Twig(),
'templates.path' => INC_ROOT . '/app/views'
]);
$app->configureMode($app->config('mode'), function() use ($app){
$app->config = Config::load(INC_ROOT . "/app/config/{$app->mode}.php");
});
require 'database.php';
require 'routes.php';
$app->container->set('user', function(){
return new User;
} );
$app->container->singleton('hash', function() use ($app){
return new Hash ($app->config);
});
$view = $app->view();
$view->parserOptions = [
'debug' => $app->config->get('twig.debug')
];
$view->parserExtensions = [
new TwigExtension
];
composer.json
{
"autoload":{
"psr-4":{
"Bixxcom\\": "app/Bixxcom"
}
},
"require": {
"monolog/monolog": "1.0.*",
"slim/slim": "~2.0",
"slim/views": "0.1.*",
"twig/twig": "~1.0",
"phpmailer/phpmailer": "~5.2",
"hassankhan/config": "0.8.*",
"illuminate/database": "~5.0",
"ircmaxell/random-lib": "~1.1"
}
}
User.php
<?php
namespace Bixxcom\User;
use Illuminate\Database\Eloquent\Model as Eloquent;
class User extends Eloquent
{
protected $table = 'users';
protected $fillable = [
'username',
'password',
'active',
'active_hash',
'recover_hash',
'remember_user',
'remember_token',
'first_name',
'last_name',
'age',
'email',
'phone',
'address',
'city',
'country'
];
}