code: function onCultureChange(fn, context, fire){
      resolveCulture.attach(fn, context);
  
      if (fire)
        fn.call(context, currentCulture);
    }
docs: Add callback on culture change.
  @param {function(culture)} fn Callback
  @param {context=} context Context for callback
  @param {boolean=} fire If true callback will be invoked with current
  culture name right after callback attachment.