Added support for animated emoji (#913)

* Added support for animated emoji

This was such a useful feature Discord, I'm glad you added this instead
of fixing bugs.

* Fix bugs in emote parser

* Added unit tests for emotes

src/Discord.Net.Rest/Entities/Messages/RestReaction.cs

@@ -18,7 +18,7 @@ namespace Discord.Rest
         {
             IEmote emote;
             if (model.Emoji.Id.HasValue)
-                emote = new Emote(model.Emoji.Id.Value, model.Emoji.Name);
+                emote = new Emote(model.Emoji.Id.Value, model.Emoji.Name, model.Emoji.Animated.GetValueOrDefault());
             else
                 emote = new Emoji(model.Emoji.Name);
             return new RestReaction(emote, model.Count, model.Me);