Refactoring debit_credit service object, prepare for additional transactions.
Set init transaction. need to save new value.
Refactor the DebitCredit methods (a lot). Catch transaction errors in the front-end.
Create init transaction showing initial number of coins for new user upon signing up.
Merge pull request #61 from paulld/init_transaction

Create init transaction recording initial number of coins. Refactor the DebitCredit service object methods.