enable mapping with scope resolution operators to be loaded

It was hard (impossible) for me to override item_wrapper_class for those radio inputs. So this is how I'd monkey patch.

user can extend (monkey patch) built in inputs.

# form.rb
<%= simple_form_for ... do |f| %>
  <%= f.input :bam, as: "extension/collection_radio_buttons" %>

# lib/inputs.rb
module Extension
  class CollectionRadioButtonsInput < SimpleForm::Inputs::CollectionRadioButtonsInput
  protected
    def item_wrapper_class
      # go crazy ...
    end
  end
end