actually create the news channels when given the type

src/Discord.Net.Rest/Entities/Channels/RestGuildChannel.cs

@@ -35,8 +35,7 @@ namespace Discord.Rest
             switch (model.Type)
             {
                 case ChannelType.News:
-                    // TODO: create new RestNewsChannel
-                    throw new NotImplementedException();
+                    return RestNewsChannel.Create(discord, guild, model);
                 case ChannelType.Text:
                     return RestTextChannel.Create(discord, guild, model);
                 case ChannelType.Voice:

src/Discord.Net.WebSocket/Entities/Channels/SocketGuildChannel.cs

@@ -49,8 +49,7 @@ namespace Discord.WebSocket
             switch (model.Type)
             {
                 case ChannelType.News:
-                    // TODO: create new SocketNewsChannel
-                    throw new NotImplementedException();
+                    return SocketNewsChannel.Create(guild, state, model);
                 case ChannelType.Text:
                     return SocketTextChannel.Create(guild, state, model);
                 case ChannelType.Voice:

src/Discord.Net.WebSocket/Entities/Channels/SocketNewsChannel.cs

@@ -13,7 +13,7 @@ namespace Discord.WebSocket
             :base(discord, id, guild)
         {
         }
-        internal new static SocketTextChannel Create(SocketGuild guild, ClientState state, Model model)
+        internal new static SocketNewsChannel Create(SocketGuild guild, ClientState state, Model model)
         {
             var entity = new SocketNewsChannel(guild.Discord, model.Id, guild);
             entity.Update(state, model);