removed wip tag from passing feature
added 'update transaction' feature and started the implementation
added logic to support updating account balances on transaction updates
added logic to handle account balance update when an account is changed on a transaction item
added a bit of a kludge to the 'update transaction' feature to make it pass
remove wip tag from passing feature
added 'delete transaction' feature
added destory method to transactions controller
completed new tests in transactions controller spec