def to_css(prefix="example", header=true)
      css_classes = self.zip(self.to_images).map do |item|
        item_filelist,item_imagefile = item[0],item[1]
        item_imagefile.as_css_background_with_class( prefix + "-#{item_filelist.pathmap('%n')}" )
      end

      header_msg = "/* Generated with CSSquirt! (http://github.com/mroth/cssquirt/) */\n"
      header_msg = '' if header == false
      header_msg + css_classes.join("\n")
    end
def to_css(prefix="example", header=true)
      css_classes = self.zip(self.to_images).map do |item|
        item_filelist,item_imagefile = item[0],item[1]
        item_imagefile.as_css_background_with_class( prefix + "-#{item_filelist.pathmap('%n')}" )
      end

      header_msg = "/* Generated with CSSquirt! (http://github.com/mroth/cssquirt/) */\n"
      header_msg = '' if header == false
      header_msg + css_classes.join("\n")
    end
Public: return a CSS document of all images

 prefix - an optional String to automatically prefix all class names with, useful
          for namespacing, etc. Default: nil.
 header - a optional Boolean value representing whether or not to include the
          "generated by" credit in the header of the CSS document. Default: true.

 Returns a CSS document as a String.