Add Kodos as a re reference.
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index 2fb93ac..270e551 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -43,6 +43,9 @@
       second edition of the book no longer covers Python at all, but the first
       edition covered writing good regular expression patterns in great detail.
 
+   `Kodos <http://kodos.sf.net/>`_
+      is a graphical regular expression debugger written in Python.
+
 
 .. _re-syntax: