Document that HalfDuplexStream is actually a "simplex" Stream

Fixes #144

src/Nerdbank.Streams.Tests/MultiplexingStreamChannelOptionsTests.cs

@@ -73,7 +73,7 @@ public void ExistingPipe_DuplexPipe()
     }
 
     [Fact]
-    public void ExistingPipe_AcceptsHalfDuplex()
+    public void ExistingPipe_AcceptsSimplex()
     {
         var options = new MultiplexingStream.ChannelOptions();
 

src/Nerdbank.Streams/HalfDuplexStream.cs

@@ -17,6 +17,7 @@ namespace Nerdbank.Streams
     /// <summary>
     /// A <see cref="Stream"/> that acts as a queue for bytes, in that what gets written to it
     /// can then be read from it, in order.
+    /// This is actually a "simplex" stream -- not a half duplex stream. Naming bug.
     /// </summary>
     public class HalfDuplexStream : Stream, IBufferWriter<byte>, IDisposableObservable
     {