Be clearer about Python version compat

We support 2.6 again, but 2.5 etc are not supported.
diff --git a/docs/index.txt b/docs/index.txt
index f8e2320..7515fe3 100644
--- a/docs/index.txt
+++ b/docs/index.txt
@@ -103,10 +103,10 @@
 
 .. index:: older versions
 
-Older Versions
-++++++++++++++
+Older Versions of Python
+++++++++++++++++++++++++
 
-Version 1.0.1 is the last version compatible with Python 2.6.
+Version 1.0.1 is the last version compatible with Python < 2.6.
 
 .. index:: maintainer notes