def with_breadcrumb(key, *args, &block)
      original_renderer = @_gretel_renderer
      @_gretel_renderer = Gretel::Renderer.new(self, key, *args)
      yield
      @_gretel_renderer = original_renderer
    end
def with_breadcrumb(key, *args, &block)
      original_renderer = @_gretel_renderer
      @_gretel_renderer = Gretel::Renderer.new(self, key, *args)
      yield
      @_gretel_renderer = original_renderer
    end
Yields a block where inside the block you have a different breadcrumb than outside.

   <% breadcrumb :about %>

   <%= breadcrumbs # shows the :about breadcrumb %>

   <% with_breadcrumb :product, Product.first do %>
     <%= breadcrumbs # shows the :product breadcrumb %>
   <% end %>

   <%= breadcrumbs # shows the :about breadcrumb %>