Remove unused 'index' argument from the Element.remove method.

Part of #2.

lib/elementtree.js

@@ -103,7 +103,7 @@ Element.prototype.insert = function(index, element)
   this._children[index] = element;
 };
 
-Element.prototype.remove = function(index, element)
+Element.prototype.remove = function(element)
 {
   this._children = this._children.filter(function(e) {
     /* TODO: is this the right way to do this? */