Stop the caddy message and start our own init notifications.
Log the version of CoreDNS when starting up.
Fix all middleware's setup functions so that return the error prefixed
with *which* middleware was failing; leads to better debuggable errors
when starting up.
Fix the code copied from Caddy to refer to Corefile and make 'coredns'
with flags pickup a local Corefile.
Also remove some references to Caddy in the docs and output of coredns.
Fixes#235
