working on InMemoryCreditCardDao
Added basic impl for AddCommand.execute + tests
Added ChargeCommand
Added ChargeCommandTest.execute_increases_card_balance_by_amount
changed return type of CreditCardDao.create from int to void and int never being used
added basic in-memory storage for InMemoryCreditCardDao
removed hard coded dummy code from InMemoryCreditCardDao.get
removing hard coded dummy code from InMemoryCreditCardDao.get
added CreditCardDao.update
removed dummy code from InMemoryCreditCardDao.get; working on ChargeCommand.execute
added basic commandParams processing for ChargeCommand
added Command.processParams and basic impl in ChargeCommand
added processParams_insufficient_params
added processParams_amount_missing$
added processParams_ok_params
introduced new NameAmountCommand so can reuse logic in ChargeCommand and CreditCommand
added CreditCard.credit + tests
added more CreditCard.credit tests
added CreditCard.charge tests
removed comments