activerecord-hackery/ransack — pull request #450 by tbuehl (2014-10-17 13:01:55+00:00)
Title: README Sort by associations fix

To sort by an association you need to use ```#{model_name}_#{attribute_name}``` instead of ```#{model_name}.#{attribute_name}```. At least for Rails 4.1.

You also need to join that association. Should I add that too?