Custom content type

Setting ctype doesn't change anything when rendering as it is always overwritten on Feed.php line 306.

$this->ctype = ($format == 'atom') ? 'application/atom+xml' : 'application/rss+xml';

This seems to be missing a check to see if it has been set before.

        if(null == $this->ctype){
            $this->ctype = ($format == 'atom') ? 'application/atom+xml' : 'application/rss+xml';
        }