DOC: update RELEASE.md to point to stable whatsnew

Author: jreback

RELEASE.md

@@ -2,5 +2,5 @@ Release Notes
 =============
 
 The list of changes to pandas between each release can be found
-[here](http://pandas.pydata.org/pandas-docs/dev/release.html). For full
+[here](http://pandas.pydata.org/pandas-docs/stable/whatsnew.html). For full
 details, see the commit logs at http://github.com/pydata/pandas.