def footer(*args, &block)
      if block_given?
        block = capture(&block)
        @footer_line.add_cell(@collection.first, args, nil, block)
      else
        @footer_line.add_cell(@collection.first, args)
      end
      nil
    end
def footer(*args, &block)
      if block_given?
        block = capture(&block)
        @footer_line.add_cell(@collection.first, args, nil, block)
      else
        @footer_line.add_cell(@collection.first, args)
      end
      nil
    end
Create a cell of footer, to have more control.
 It can be called with or without a block.
 The three exemples are equivalent:

  # With a block:
  <% sorting_table_for @users do |table| %>
    <%= table.footers do %>
      <%= table.footer :username %>
      <%= table.footer :firstname %>
    <% end %>
  <% end %>

  # With a block:
  <% sorting_table_for @users do |table| %>
    <%= table.footers do %>
      <%= table.footer do %>
        <%= :username %>
      <% end %>
      <%= table.footer do %>
        <%= :firstname %>
      <% end %>
    <% end %>
  <% end %>

 === Options

 * :html - Hash options: class, id, ...
 * :caption - set caption on td

  # Exemples:
  <% sorting_table_for @users do |table| %>
    <%= table.columns :username, :cation => 5 %>
  <% end %>

 === I18n

 Add a value on scope for footer. Only with symbol.

  # Exemple of i18n_add_header_action_scope:
  SortingTableFor::TableBuilder.i18n_add_footer_action_scope = :footer

  # Ouput:
  I18n.t(:edit, :scope => [:current_controller, :current_action]) => en.current_controller.current_action.footer.edit

 With block the value won't be interpreted.