def map_export_data(collection, options={})
        # Use :only and :except options or else use class defaults for columns.
        if !options[:only].blank?
          options[:columns] = Array.wrap(options[:only]).map(&:to_sym)
        elsif !options[:except].blank?
          options[:columns] = column_names.map(&:to_sym) - Array.wrap(options[:except]).map(&:to_sym)
        else
          options[:columns] = exportable_options[:columns]
        end
        if options[:columns].empty?
          raise MakeExportable::ExportFault.new("You are not exporting anything")
        end
        # TODO: Go ahead and humanize/titleize the column names here
        headers = options[:columns].map(&:to_s)
        rows = collection.map do |item|
          options[:columns].map {|col| item.export_attribute(col) }
        end
        return rows.unshift(headers)
      end
def map_export_data(collection, options={})
        # Use :only and :except options or else use class defaults for columns.
        if !options[:only].blank?
          options[:columns] = Array.wrap(options[:only]).map(&:to_sym)
        elsif !options[:except].blank?
          options[:columns] = column_names.map(&:to_sym) - Array.wrap(options[:except]).map(&:to_sym)
        else
          options[:columns] = exportable_options[:columns]
        end
        if options[:columns].empty?
          raise MakeExportable::ExportFault.new("You are not exporting anything")
        end
        # TODO: Go ahead and humanize/titleize the column names here
        headers = options[:columns].map(&:to_s)
        rows = collection.map do |item|
          options[:columns].map {|col| item.export_attribute(col) }
        end
        return rows.unshift(headers)
      end
<tt>map_export_data</tt> takes a collection and outputs an array of arrays representing
 the rows and columns of the export data. The first item ("row") in the array will be
 an array of strings to be used as column headers.
 Valid options include :only and :except.
 See <tt>to_export</tt> for more details on the options.

   User.map_export_data(User.visible, :only => [:first_name, :last_name, :username])
   # => [['first_name', 'last_name', 'username'], ['John', 'Doe', 'johndoe'], ...]