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.WebSocket/DiscordSocketClient.cs

@@ -365,7 +365,7 @@ namespace Discord.WebSocket
             await ApiClient.SendStatusUpdateAsync(
                 status,
                 status == UserStatus.AFK,
-                statusSince != null ? DateTimeUtils.ToUnixMilliseconds(_statusSince.Value) : (long?)null,
+                statusSince != null ? _statusSince.Value.ToUnixTimeMilliseconds() : (long?)null,
                 gameModel).ConfigureAwait(false);
         }