added carousel widget

Example of use:

```php
echo Carousel::widget(array(
	'items' => array(
		array(
			'src' => 'http://twitter.github.io/bootstrap/assets/img/bootstrap-mdo-sfmoma-01.jpg',
		),
		array(
			'src' => 'http://twitter.github.io/bootstrap/assets/img/bootstrap-mdo-sfmoma-02.jpg',
			'captionLabel' => 'This Rocks',
			'captionText' => 'This is the caption text and also ROCKS!'
		)
	),
	'options' => array('style'=>'width:870px')
));
```

closes #331