code: function(n, r) {
          r = r || 0;
          var nodes = [];
          NodeList.each(this, function(node, i) {
              if (i % n === r) {
                  nodes.push(node);
              }
          });
  
          return Y.all(nodes);
      }
docs: Creates a new NodeList containing all nodes at every n indices, where
  remainder n % index equals r.
  (zero-based index).
  @method modulus
  @param {Int} n The offset to use (return every nth node)
  @param {Int} r An optional remainder to use with the modulus operation (defaults to zero)
  @return {NodeList} NodeList containing the updated collection