update whatsnew

Author: wholmgren

docs/sphinx/source/whatsnew/v0.2.0.txt

@@ -11,7 +11,7 @@ We recommend that all users upgrade to this version.
 API changes
 ~~~~~~~~~~~
 
-
+* Change variable names to conform with new `Variables and style rules wiki <https://github.com/pvlib/pvlib-python/wiki/Variables-and-style-rules>`_ (:issue:`37`, :issue:`54`).
 
 Enhancements
 ~~~~~~~~~~~~