ree-1.8.7-2010.02 > s = Site.last
 => #<Site _id: 4cd42b3f9b55d827de000005, theme: "default", site: "localhost">
ree-1.8.7-2010.02 > s.midias.create(:image => my_file, :kind => 'teste')
 => #<Midia _id: 4cd42b779b55d827de000006, kind: "teste", image_filename: "wallpaper_bruno.png", image: nil>
ree-1.8.7-2010.02 > s.save
 => true
ree-1.8.7-2010.02 > Site.last.midias
 => []