Add DtDNS as new provider.
Catch various network/server errors.
Log which configuration file is loaded.
Remove some code duplication for guessing IP addresses.
ddns: Add guess-ip-addresses command.

This will show the guessed external IP addresses for IPv6 and IPv4.
Install a sample configuration file.
Update .gitignore.
Merge remote-tracking branch 'stevee/dtdns.com'