title: How can I extend the Set object in Snap
body: <p>I am trying to convert a large body of code from Raphael to Snap.
  I am coming across a number of problems - I will ask 1 question for each, to avoid thread confusion.</p>
  
  <p>I have a number of calls to the Raphael toFront method. This method is missing from Snap, but I found a suggested implementation:</p>
  
  <pre><code>Snap.plugin(function (Snap, Element, Paper, glob) {
      var elproto = Element.prototype;
      elproto.toFront = function () {
          this.appendTo(this.paper);
          return this;
      };
      elproto.toBack = function () {
          this.prependTo(this.paper);
          return this;
      };
  });
  </code></pre>
  
  <p>This is all very fine for Elements, but I find most of my toFront calls are on sets. Is there a way to extend the Snap set?</p>