fix mockServer to always provide change list sequence numbers

mock_server.go

diff --git a/mock_server.go b/mock_server.go
index 7fc488e..53f6c2c 100644
--- a/mock_server.go
+++ b/mock_server.go
@@ -678,6 +678,10 @@
 // create []common.Table from array of tableRowMaps
 func (m *MockServer) concatChangeLists(changeLists ...common.ChangeList) common.ChangeList {
 	result := common.ChangeList{}
+	if len(changeLists) > 0 {
+		result.FirstSequence = changeLists[0].FirstSequence
+		result.LastSequence = changeLists[len(changeLists)-1].LastSequence
+	}
 	for _, cl := range changeLists {
 		for _, c := range cl.Changes {
 			result.Changes = append(result.Changes, c)