Responsive tables (add cell description -- data attribute)

Add cell description.js

function pridatPopisky(el) {
  var popisky = el.getElementsByTagName("th");
  var radky = el.getElementsByTagName("tr");
  for (var i = 1; i < radky.length; i++) {
    var bunky = radky[i].getElementsByTagName("td");
    for (var j = 0; j < bunky.length; j++) {     
      bunky[j].setAttribute("popisek", $(popisky[j]).html());
    }
  }
}