title: Leaflet Control.Layers wrong checked state
body: <p>I'm using LayerGroups and I want to be able to show/hide those groups with a <a href="http://leafletjs.com/reference.html#control-layers" rel="nofollow">layers control</a></p>
  
  <p>The several LayerGroups appear on the map but the associated checkbox for each one is unchecked by default, if I click once in the checkbox it behaves properly.</p>
  
  <p><a href="http://fairuaweb.s3-website-eu-west-1.amazonaws.com/" rel="nofollow">Here's the project</a></p>
  
  <p>How can I do to make the checkboxes checked by default?</p>