It is impossible to send a check-in receipt

[orenyk]

The way our code is currently set up, we automatically send a check-out receipt e-mail when an item is picked up but not when it is returned. Instead, upon return, we show them a receipt page that has a button labeled Email return receipt that hits the reservations#send_receipt action (this is also the action that is triggered by hitting the similarly named buttons on the reservation show page. However, this action is hard-coded to only send a check-out receipt. We should fix this.

[orenyk]

Tweaking the controller to fix this - it isn't pretty but it's fine for now.