page_menu are now with uniquie id

let me start from the beginning . 
When you use this gem with `2.0.5` version and put the following things in 
`$cat config/initializers/refinery/page_menus.rb` 

    Refinery::PageMenus.configure do |config|
     config.menu_resources = {:refinery_page=>
      { klass: 'Refinery::Page',
                            title_attr: 'title',
                            admin_page_filter: {
                                draft: false
                            }
        }
      }   
    end
Then, when you goes to `http://0.0.0.0:3000/refinery/page_menus/1/edit` where `1` is id of `page_menus` which you like to edit .
Now  add 5-6 `Refiney Pages` into it and try changing its labels. Now checks menus either by going frontend or open same edited file . You will see that only one menu has changed its label. 
So, **this the bug** . 
And this is the fix for it .