add message about python 2.7

Probably does not work for python < 3.4

Author: robkooper

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## 2.3.1 - 2020-09-18
 
+With this version we no longer gurantee support for versions of python below 3.
+
 ### Fixed
 - There was an issue where status messages could cause an exception. This would prevent most extractors from running correctly.