Add Phalcon\Chart\QRcode

```php
$str = 'Phalcon is web framework';

$qr = new \Phalcon\Chart\QRcode();
$ret = $qr->generate($str);
var_dump($ret);

if ($ret) {
	$data = $qr->render();

	$ret = $qr->save('unit-tests/assets/qr.png');

	$ret = $qr->scan('unit-tests/assets/qr.png');

	$data = $qr->render(NULL, NULL, 'FFCC00', '000000');

	$ret = $qr->save('unit-tests/assets/qr2.png', NULL, NULL, 'FFCC00', '000000');
}
```