Add getBalanceSheet() to RippleAPI

test/mock-rippled.js

@@ -283,5 +283,9 @@ module.exports = function(port) {
     setTimeout(() => conn.send(response), 20);
   });
 
+  mock.on('request_gateway_balances', function(request, conn) {
+    conn.send(createResponse(request, fixtures.balance_sheet));
+  });
+
   return mock;
 };