Testing out Shippable CI.
I think this finally sorts out DNS resolving edge-case oddities.

Now the dns resolver should always trigger changes when new IPs are
seen, even if those IPs had been seen previously (we were
unintentionally keeping all recently seen IPs in memory which we don't
want anymore for hosts we're not caching).
Allow the global rate limits applied in nginx to be configurable.
Merge branch 'master' into gsa