belatedly add news entry for issue #8 fix

docs/news.txt

@@ -10,6 +10,9 @@ tip
 * Allow packages to be upgraded, e.g., ``pip install Package==0.1``
   then ``pip install Package==0.2``.
 
+* Allow installing/upgrading to Package==dev (fix "Source version does not
+  match target version" errors).
+
 * Fixed a bug with pip install --download and editable packages, where
   directories were being set with 0000 permissions, now defaults to 755.