Be sure to disable pull-ups on PORTB

Individual pull-ups are enabled by default if !RABPU is enabled.
Swap RA3 and RA4 function.

This was an error, RA3 is input only! So, external led is controlled via RA4
(there's a current limiting resistor attached to it in the schematics, too) and
RA3 is the lid sensor input.
Add comment explaining change in OPTION_REG.