Animated Gif support

[dtonon]

Currently gif are not supported, only the first frame is shown. I'm absolutely not a fan of lazy-animated-memes, but sometime gifs are a quick and useful way to share short/simple animation.

But first, there is a usability problem: by showing only the first frame, the poster's message could be completely misunderstood. Let's think about a GIF that starts with a provocative message, and then explains the meaning. The Gossip user will receive half the information, and this could create many problems.

@bu5hm4nn did you already check on this matter in the past?