Users can use link to confirm their pickup

https://trello.com/c/QdJFf7qp/12-as-a-user-i-can-confirm-my-pickup-using-a-button

![userconfirm](https://cloud.githubusercontent.com/assets/8646429/5114923/0f9221d6-700b-11e4-9120-5946efbeb8f8.gif)

these two lines can be:

``` ruby+  
def create
   pickup = find_pickup_from_url
  pickup.update(confirmed: true)
  ...
end
```