Fix tree encoding to save more bits
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 10ce75a..a1800be 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -1,5 +1,6 @@
 Mark Adler
 Jyrki Alakuijala
+Frédéric Kayser
 Daniel Reed
 Huzaifa Sidhpurwala
 Péter Szabó