message: fix snapshot of intervals
diff: @@ -30,7 +30,7 @@ export class Interval implements Collections.IInterval {
  public serialize(client: MergeTree.Client) {
  let startPosition = this.start.toPosition(client.mergeTree,
  client.getCurrentSeq(), client.getClientId());
  - let endPosition = this.start.toPosition(client.mergeTree,
  + let endPosition = this.end.toPosition(client.mergeTree,
  client.getCurrentSeq(), client.getClientId());
  let serializedInterval = <ISerializedInterval>{
  endPosition,
  