Admin items presenters

Hi @joneslee85 

I added the presenter as you did in the normal Items Controller -> this uses it for @items, and it was fine.

But I'm not sure about extending it for @item as well.

I tried to set it as item = Item.find(param[:id]) in the presenter, but that wasn't working.

I have watched this http://railscasts.com/episodes/287-presenters-from-scratch -> is this something I should be learning from? 
move the logic to controller (see my explanation above)