Cache the size and the do bit whenever someone asked for it. We can
probably add more:
PASS
BenchmarkStateDo-4 100000000 11.9 ns/op
BenchmarkStateSize-4 5000000 265 ns/op
ok github.com/miekg/coredns/middleware 2.828s
PASS
BenchmarkStateDo-4 1000000000 2.86 ns/op
BenchmarkStateSize-4 500000000 3.10 ns/op
ok github.com/miekg/coredns/middleware 5.032s
This PR also includes some testing cleanups as well.
Add a test for SkyDNS':
https://github.com/skynetservices/skydns/issues/217
Put the CNAME in front for both answer and extra sections. Note that
the etcd middleware seems to already to the correct thing though.
