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

test/Discord.Net.Tests/Tests.Emotes.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using Xunit;
 
 namespace Discord
@@ -34,6 +34,7 @@ namespace Discord
             Assert.Equal(DateTimeOffset.FromUnixTimeMilliseconds(1514056829775), emote.CreatedAt);
             Assert.EndsWith("gif", emote.Url);
         }
+        [Fact]
         public void Test_Invalid_Amimated_Emote_Parse()
         {
             Assert.False(Emote.TryParse("<x:typingstatus:394207658351263745>", out _));