DOC: release notes re: #921

Author: wesm

RELEASE.rst

@@ -132,6 +132,8 @@ pandas 0.8.0
     404s (#826)
   - Improve performance of reshaping by using O(N) categorical sorting
   - Series names will be used for index of DataFrame if no index passed (#1494)
+  - Header argument in DataFrame.to_csv can accept a list of column names to
+    use instead of the object's columns (#921)
 
 **API Changes**