[FEATURE] add fixed fee to payment API
Merge pull request #239 from boxbag/transaction-fixed-fee

[FEATURE] add fixed fee to payment API
[FEATURE]: Balances|Trustlines: Refactor with promises and allow limit=all
Merge pull request #240 from lumberj/feature/unpaginated_balances_and_trustlines

[FEATURE]: Balances|Trustlines: Non-paginated responses (RLJS-145)