Doranku

Thanks for this simple but useful bot. Only thing missing IMHO is persistence of the list. My Q&D hack: [toDoBot.diff.txt](https://github.com/xdavidhu/toDoBot/files/1575631/toDoBot.diff.txt)

PdnsApiAuthenticator update_soa increments the serial in the SOA content even if the value is 0. 0 is a special value where the serial is bases on the latest change_date from...