Fix Manager leak while reconnecting. (#107)

- Manager.Cleanup() does not cleanup the queue.
    - While reconnecting, not items are added to Manager.Subs, but never cleared

Author: gamlerhart

Src/SocketIoClientDotNet.net45/Client/Manager_net35.cs

@@ -419,6 +419,7 @@ private void Cleanup()
                 {
                     sub.Destroy();
                 }
+                Subs.Clear();
             }
         }