Ruby 1.8 doesn't support public_send. Monkey patch on Object.
Also test on ruby 1.8.7.
Rails 2 doesn't have ActiveSupport::Concern. Use `self.included`.
Rails 2 doesn't define `constantize`. Implement `class_from_string`.
ActiveSupport < 3 may cause ArgumentError when used with anonymous class (e.g. Struct) as value for `policy`.
At least Rails 2 required.
Rails 2 doesn't have ActiveModel::Naming. Remove dependency.
Test normal Gemfile and Rails 2.3 specific Gemfile.
Ignore all Gemfile*.lock files.