Add 3.1.x series header

Author: tomchristie

docs/topics/release-notes.md

@@ -38,7 +38,7 @@ You can determine your currently installed version using `pip freeze`:
 
 ---
 
-## 3.0.x series
+## 3.1.x series
 
 ### 3.1.1
 
@@ -63,6 +63,10 @@ You can determine your currently installed version using `pip freeze`:
 
 For full details see the [3.1 release announcement](3.1-announcement.md).
 
+---
+
+## 3.0.x series
+
 ### 3.0.5
 
 **Date**: [10th February 2015][3.0.5-milestone].