gregbell/active_admin — pull request #3064 by jgorset (2014-04-09 20:12:15+00:00)
Title: Use `sort_by` instead of `sort_by!`

`sort_by!` and other mutator methods are blacklisted as of Ruby on Rails
4.1.0.rc2 and now yield `NoMethodError`.

References:
* https://github.com/rails/rails/commit/d4ee09c