code: function append() {
    var i, l = this.length, el, args = this.slice.call(arguments);
    function it(node, index) {
      // content elements to insert
      el.each(function(ins) {
        ins = (index < (l - 1)) ? ins.cloneNode(true) : ins;
        node.appendChild(ins);
      });
    }
    for(i = 0;i < args.length;i++) {
      // wrap content
      el = this.air(args[i]);
      // matched parent elements (targets)
      this.each(it);
    }
    return this;
  }
docs: Insert content, specified by the parameter, to the end of each
  element in the set of matched elements.