Even though #print_more will display nothing since ''.split("\n").each()
iterates 0 times, it will still be called without this modifier which is
unnecessary.
This cleans up the API a bit by removing the requirement of placing #run
inside a Thread.new {EventMachine.next_tick {}} block. That should not
be the caller's responsibility.
Previously, upstream nameservers were configured by default even if the
config file did not specify them. Now upstream nameservers are only
used if they are specified. If none are given, then NXDOMAIN is
returned for unresolvable requests.
Even though it is unlikely that a user would remove these options from
the DNS config file, it is still good practice to have these safeguards
in place.
Many filter checks were removed because the new DNS extension performs
validation before performing any database operation.
Modified message for InvalidParamError to be more modular.
