$(function(){
  var slider = $('#slider-portfolio').bxSlider({
    controls: false,
    displaySlideQty: 6,
    moveSlideQty: 3
  });

  $('#go-prev').click(function(){
    slider.goToPreviousSlide();
    return false;
  });

  $('#go-next').click(function(){
    slider.goToNextSlide();
    return false;
  });
});