update changelog for 0.2.3

Author: rinatkhaziev

readme.txt

@@ -309,6 +309,11 @@ Flush the cache when adding or deleting ad codes, and set priority of 10 when a
 
 == Changelog ==
 
+= 0.2.3 (June 25,2012) =
+
+* Allow columns to be optional when creating and editing ad codes, introduced new filter acm_ad_code_args
+* Remove acm_provider_columns filter
+
 = 0.2.2 (June 5, 2012) =
 * New Google Ad Sense provider courtesy of [Erick Hitter](http://www.ethitter.com/)
 * Bulk delete action added for the WP List Table of ad codes. Delete more ad codes in one go