Preprocess transaction before submit

Because stellard returns tesSUCCESS when you submit a transaction that will error will a tem* error on ledger apply, and then doesn't check to see if that transaction hash is around when you resubmit the same error transaction, we need to check if the transaction hash exists before we submit a tranasaction and see if it resulted in a tem* error manually, everytime before we submit a transaction. :(

To be fixed in https://github.com/stellar/stellard/issues/173