DOC: release notes

Author: wesm

RELEASE.rst

@@ -183,6 +183,7 @@ pandas 0.8.0
   - Fix MultiIndex partial indexing bug (#1352)
   - Enable assignment of rows in mixed-type DataFrame via .ix (#1432)
   - Reset index mapping when grouping Series in Cython (#1423)
+  - Fix outer/inner DataFrame.join with non-unique indexes (#1421)
 
 pandas 0.7.3
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