Added a note about Duality not being supported any more

zvonimir · zvonimir · commit d17d6475d1e6 · 2019-07-15T21:18:22.000-06:00
To avoid confusion in the future. Closes #459
diff --git a/docs/demos.md b/docs/demos.md
@@ -2,5 +2,6 @@
 
 
 A narrated introduction and demonstration of SMACK can be seen at
-https://youtu.be/SPPSC1KdRzs
+https://youtu.be/SPPSC1KdRzs. Note that the demo is somewhat outdated; for
+example, Duality is no longer supported.
 
