Elements not inserted correctly

[dcpesses]

When the Element.insert method is called, the element is not actually inserted into the array. Instead, it overwrites the existing element at that index.

See https://github.com/racker/node-elementtree/blame/master/lib/elementtree.js#L101

Element.prototype.insert = function(index, element)
{
  this._children[index] = element;
};

Instead, line 103 should be changed to this._children.splice(index, 0, element);