activeadmin/activeadmin — pull request #3540 by timoschilling (2014-10-30 13:53:37+00:00)
Title: Setting with questionmark

add support for `config.setting_name?`

This adds a ActiveModel like questionmark attr checker:
```ruby
inheritable_setting :foo, true
config.foo? # => true

inheritable_setting :foo, false
config.foo? # => false

inheritable_setting :foo, ""
config.foo? # => false

inheritable_setting :foo, "bar"
config.foo? # => true
```