code: function(suffix) {
          return function(now, tween) {
            var floored_number = Math.floor(now),
                target = $(tween.elem);
  
            target.prop('number', now).text(floored_number + suffix);
          };
        }
docs: Creates numberStep handler, which appends string to floored animated number on each step.
  
  @example
  // will animate to 100 with "1 %", "2 %", "3 %", ...
  $('#someid').animateNumber({
  number: 100,
  numberStep: $.animateNumber.numberStepFactories.append(' %')
  });
  
  @params {String} suffix string to append to animated number
  @returns {Function} numberStep-compatible function for use in animateNumber's parameters