- add many motivation, helpful comments and important details
- improve formatting through use of more native sphinx/rst elements, like
the csv-table for DNS records
- clarify the basic requirements
- use dig for uncached DNS propagation checks against an authoritative
nameserver
- explain the basic feature set of the setup example
- adjust DNS TTLs; 1h is a common duration in modern setups and does not
hurt caching much
- remove mention of the announce mailinglist, users can just expect
releases to be ready around branch-off