we should set tail to undef by default, so the module can be used without needing to set that option See merge request !2
according to an ally at Google, they do not correlate logs of queries to those nameservers and anonymise logs after 24 hours. therefore we consider it an acceptable tradeoff between reliability, availability and privacy. note that the previous default (presumably Immerda's nameservers) were not reachable while doing this commit so could not be tested for availability.
this uses the resolvconf package from Debian, so may not be portable everywhere
this is useful in Linux to add an 'options' line