message: add paymentHistory to xrp-client-interface
diff: import { Wallet } from 'xpring-common-js'
  import { BigInteger } from 'big-integer'
  import TransactionStatus from './transaction-status'
  +import XRPTransaction from './model/xrp-transaction'
  /**
  * An interface describing XRPClient.
  @@ -46,4 +47,16 @@ export default interface XRPClientInterface {
  * @returns A boolean if the account is on the ledger.
  */
  accountExists(address: string): Promise<boolean>
  +
  + /**
  + * Return the history of payments for the given account.
  + *
  + * Note: This method only works for payment type transactions, see: https://xrpl.org/payment.html
  + * Note: This method only returns the history that is contained on the remote node, which may not contain a full history of the network.
  + *
  + * @param address: The address (account) for which to retrive payment history.
  + * @throws: An error if there was a problem communicating with the XRP Ledger.
  + * @return: An array of transactions associated with the account.
  + */
  + paymentHistory(address: string): Promise<Array<XRPTransaction>>
  }
  