Clarify the comments in the codelab.

Jacob had some good questions.  Help the next person.

Change-Id: I03de05e0930c95ba46129917d39a71b2f077208e
diff --git a/frc971/codelab/basic.cc b/frc971/codelab/basic.cc
index 36e64c5..6144fed 100644
--- a/frc971/codelab/basic.cc
+++ b/frc971/codelab/basic.cc
@@ -30,7 +30,8 @@
     Status::Builder builder = status->MakeBuilder<Status>();
     // TODO(you): Fill out the Status message! In order to populate fields, use
     // the add_field_name() method on the builder, just like we do with the
-    // Output message above.
+    // Output message above.  Look at the definition of Status in
+    // basic_status.fbs and populate the field according to the comments there.
 
     status->Send(builder.Finish());
   }