Usage:
$().retina([settings]);

  settings:
  A set of key/value pairs. All settings are optional.
  
    retina-background (default: false)
    Whether to change background image to high resolution.
    
    retina-suffix (default: @2x)
    The suffix for high resolution image file.

Example:
<script src="jquery.retina.js" type="text/javascript"></script>
<script type="text/javascript">
$(function() {
  $(".retina").retina({"retina-background":true});
});
</script>