accepter les images de tous formats

exemples : webp / http://1-ps.googleusercontent.com/h/www.vincentabry.com/wp-content/uploads/2013/07/650x433xOndes-WiFi.jpg.pagespeed.ic.1SQ0YgjZYq.webp http://seenthis.net/messages/159006

bmp / http://3.bp.blogspot.com/-1VnqDvh1WnU/UAS6rvOFrCI/AAAAAAAABCg/gRsfgDMUkS8/s1600/bingo.bmp http://seenthis.net/messages/174420