Fix a traversal class not serializable error.

EduNetworkBuilder/NetworkBuilder.cs

@@ -2206,6 +2206,7 @@ namespace EduNetworkBuilder
 
         private void optionsToolStripMenuItem_Click(object sender, EventArgs e)
         {
+            ProcessChange(); //make sure we make an undo-point in case a change is made.
             OptionsWindow tWindow = new OptionsWindow(myNetwork);
             tWindow.ShowDialog();
             myNetwork.UpdateDeviceSizes();

EduNetworkBuilder/TraversalClass.cs

@@ -9,6 +9,7 @@ namespace EduNetworkBuilder
     [Serializable]
     public class TraversalClass
     {
+        [Serializable]
         protected struct TraversalRecord
         {
             public string host;