The player may now pick up and use objects. new commands implemented are the
ones specified in the assignment description. The only change is that instead
of ESC cancelling an inventory operation, any key other than the valid
selectors will cancel the operation.

Since stacks are not implemented, the player is not allowed to drop an item
when they are already standing on top of one.

Combat displays the attacked monsters remaining hp, and the players remaining
hp. Monster names are not displayed as that was not required.

Player speed has a minimum of 1 to avoid divide by 0 errors.