Allow specifying a primary server and retrieve the zone's content.

Add tests and an Expired bool to zone struct, to stop server zones

that are expired. The zone is retrieved on Startup, no updates of

changed content are done. We also don't respond to notifies yet.

Some doc updates and tweaks.

This adds a bunch of supporting code to send notifies to a primary

name server.

Change from SERVFAIL to diff. between error and no such zone hosted.

Fixes: #68

Drop the use of dns.RR when in fact the only thing we use is the name

and type of the RR. Cleans up a bunch of stuff and also stops the weird

making of dns.RRs just for a lookup. Should safe some memory as well.



Fixes: #66

When looking for a name in tree, return wether we got to a longer one -

if so we had an ent. Add tests + dnssec tests and refactor the tests as

well a bit.

middleware: change documentation filenames to README.md

Add benchmark for normal and DNSSEC lookup. We can probably shave quite
a lot of these, but first lets actually get to something that is
serving.

Positive wildcare replies

Reply to queries when you have a wildcard in the zone. This works
for DNS and DNSSEC. Thing missing is NODATA responses for that specific
wildcard.

Add wildcard_test.go as well.

Get positive dnssec stuff going

Add canonical sorting

Add a low-allocation canonical sorting function that can be used in
middleware.

This implements the tests from rfc4034 correctly.

Transfer out

These can be enabled by adding "transfer out" to the Corefile. Without
it no AXFR is allowed.

For now only AXFR and no IXFR. No TSIG and no ACLs.

Add testing package

This already includes a bunch of helper functions that aid in testing.
Factor out etcd and file testing to use this package.

Fixes: #50

Etcd stub