Unwrapped thrown exceptions

Developers were getting wrapped exceptions which were not very
distinguishable and required a lot of digging to pull out the base
exception which is the most relevant piece.

SignalR.Client/Connection.cs

@@ -229,7 +229,7 @@ private Task Negotiate(IClientTransport transport)
                     if (task.IsFaulted)
                     {
                         Stop();
-                        tcs.SetException(task.Exception);
+                        tcs.SetException(task.Exception.Unwrap());
                     }
                     else if (task.IsCanceled)
                     {