introduce check_other and radio_other question types

completes issue #48

app/helpers/application_helper.rb

@@ -22,7 +22,9 @@ module ApplicationHelper
     options_for_select([
                          %w(Text text),
                          %w(Radio radio),
+                         ['Radio with other', 'radio_other'],
                          %w(Checkbox checkbox),
+                         ['Checkbox with other', 'checkbox_other'],
                          %w(Coder live_code)
                        ], selected: (val.blank? ? '' : val))
   end