Using assetic with last releases

Hello!

I'm looking for a way to use Assetic with CSS in Sonata Admin, now the files are load like this:
```twig
{% for stylesheet in admin_pool.getOption('stylesheets', []) %}
    <link rel="stylesheet" href="{{ asset(stylesheet) }}">
{% endfor %}
```

I would like to use csswrite to load css files, compress and the other reason it that I'm trying to load my static files to Amazon S3 and the paths inside css like Glyphicons in bootstrap don't load when I add css files prefixed by `assets_base_url`