pre-render footer macro needs controller sometimes

[catmando]

this patch does it all: please incorporate:

module React
  # make it so the prerender_footer macro will receive the controller
  module IsomorphicHelpers
    def self.prerender_footers(controller = nil)
      footer = Context.prerender_footer_blocks.collect { |block| block.call controller }.join("\n")
      if RUBY_ENGINE != 'opal'
        footer = (footer + @context.send_to_opal(:prerender_footers).to_s) if @context
        footer = footer.html_safe
      end
      footer
    end
  end
end
module ReactiveRuby
  module Rails
    # pass controller to the prerender_footers method
    class ComponentMount < React::Rails::ComponentMount
      def footers
        React::IsomorphicHelpers.prerender_footers(controller)
      end
    end
  end
end