Before, `getBinary` did not work for 13 sector disks because it
assumed that all tracks had 16 sectors. On top of that, `readSector`
could not decode sectors with 5 and 3 encoding. And finally,
`findSector` couldn't even find sectors with DOS 3.2 address fields.
All of these have been fixed and some tests added to make sure that
they keep working.
