update 2.4.0 readme

README.md

@@ -44,6 +44,12 @@ Requirements
 * Selenium is required on OSX: brew install selenium-server-standalone (See https://github.com/shvets/selenium)
 
 
+ActiveRecord
+-----------
+ActiveRecord was used to replace DataMapper, and now ruby 2.4 is no longer supported.
+If you're using ruby 2.4 please update your BeEF version, otherwise master-0.4.7.3 has the beef branch before the ActiveRecord Merge.
+
+
 Quick Start
 -----------