UIDs returned by -a don't work with -u

[Sigafoos]

The UIDs were added in #52 (and thank you for that!), but the UIDs being displayed don't seem to work when setting with -u:

❯ switchaudiosource -c -f json
{"name": "MacBook Pro Speakers", "type": "output", "id": "75", "uid": "BuiltInSpeakerDevice"}
❯ switchaudiosource -u BuiltInSpeakerDevice
Could not find an audio device with UID "BuiltInSpeakerDevice" of type output.  Nothing was changed.