Update Dependencies and support NS2.0 builds (#1046)

* Update deps, fix test warnings.

* Support ns2.0

* Fix typo

* Remove ns1.1 support

* Net.Http and Net.Websockets.Client are not needed in ns2.0

* Move to net46 per volt

* Remove ns1.3 constants

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

@@ -168,7 +168,6 @@ namespace Discord.Rest
             return RestUserMessage.Create(client, channel, client.CurrentUser, model);
         }
 
-#if FILESYSTEM
         public static async Task<RestUserMessage> SendFileAsync(IMessageChannel channel, BaseDiscordClient client,
             string filePath, string text, bool isTTS, Embed embed, RequestOptions options)
         {
@@ -176,7 +175,7 @@ namespace Discord.Rest
             using (var file = File.OpenRead(filePath))
                 return await SendFileAsync(channel, client, file, filename, text, isTTS, embed, options).ConfigureAwait(false);
         }
-#endif
+
         public static async Task<RestUserMessage> SendFileAsync(IMessageChannel channel, BaseDiscordClient client,
             Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options)
         {