Merge branch 'patch-1' of https://github.com/antonmoiseev/RestSharp

Author: ayoung

RestSharp/RestClient.Async.cs

@@ -46,11 +46,12 @@ public virtual RestRequestAsyncHandle ExecuteAsync(IRestRequest request, Action<
 			var http = HttpFactory.Create();
 			AuthenticateIfNeeded(this, request);
 
-			ConfigureHttp(request, http);
-
 			// add Accept header based on registered deserializers
 			var accepts = string.Join(", ", AcceptTypes.ToArray());
 			AddDefaultParameter("Accept", accepts, ParameterType.HttpHeader);
+
+			ConfigureHttp(request, http);
+
 			HttpWebRequest webRequest = null;
 			var asyncHandle = new RestRequestAsyncHandle();