title: Telegram Bot update_id in getupdate methods sometimes jumps
body: <p>I have joined a bot in a group to archive the messages. I'm coding a php code for archiving, till this get complete, I manually getupdates from the browser. and save the results in a text file. and frequently I use offset to get newer msgs. but next time when I getupdates after offset (for example one after that) I see that I have a jump! for example if the last id was 1500, after getupdate I see 1553 or 1540, and I donn't see the msgs in the gap. anyone can help me,please?</p>