Fix thumbnaisl not showing

A minor omission was made that didn't allow thumbnails to show. For completeness thumbnails really should show.

To fix this yourself just add styles and a new hash to `to_jq_upload` like so:

    class Upload < ActiveRecord::Base
      attr_accessible :upload
      has_attached_file :upload,
        styles: { 
          original: "600x600>", 
          thumbnail: "40x40#" 
        }
  

      include Rails.application.routes.url_helpers

      def to_jq_upload
        {
          "name" => read_attribute(:upload_file_name),
          "size" => read_attribute(:upload_file_size),
          "url" => upload.url(:original),
          "delete_url" => upload_path(self),
          "delete_type" => "DELETE",
          "thumbnail_url" => upload.url(:thumbnail)
        }
      end

    end