ledger.py: before this change, the second line of a ledger was a space separated list of people, but it wasn't used foranything, so we simpy remove it
Rename variable 'persona' to 'payer'
ledger.py: read first line as ledger's title
ledger.py: use main call as CLI instead of a non useful test
Remove ledger_cli.py since its functionality has been replaced by the main call of ledger.py
ledger.png: new icon