[TASK] refactor getTransactionHelper
[TASK] rename paymentIsValid to isPaymentValid
[TEST] refactor fixtures
[TASK] add validated query parameter to submit payment route
[TASK] remove unused remote
[FIX] fix code corresponding to comments in pull request
[TASK] rename getTransactionHelper to getTransaction and getTransaction to getTransactionAndRespond in transaction.js locally. Did not modify express route
[FIX] account for submission error case with validated="true" flag set
[TEST] fix typo
Merge pull request #192 from boxbag/payments-validated

[FEATURE] add validated query parameter to submit payment route
[FEATURE] allow payer to set max_fee in POST /payments request JSON body
[TEST] add test for case when payer set max fee is below computed fee
[TEST] update test case wording
[TEST] fix test grammar error
[FIX] fix typo