Edit config files
Copy ActiveRecord::Enum to Rails3Enum

from: https://github.com/rails/rails/blob/v4.1.5/activerecord/lib/active_record/enum.rb
Modified `Enum` for rails3

* Remove `detect_enum_conflict!` method
`dangerous_class_method?` is not defined on rails3.

* Use `update_attributes!` instead of `update!`
`update!` is not defined on rails3.