Properly handle the death of the player's body while their mind is in a robot.
Roomba picking stuff up -- pick up messages now customized for
room. Robots by default cannot pickup.

Decided they should have smaller inventory so tweaked inventory
class to allow for variable-sized inventories. add_item() wasn't always
returning the slot picked, which meant now that I'm displaying the
letter in the pickup message, it would crash in some cases.