Also adds thorough tests

We hit this bug internally. It generally needed to be fix and was a larger
potential problem than expected since it was assuming TD assocaitions rather
than looking at them directly. Test changes were a little involved to suss
out, otherwise this is a fairly clean and simple fix.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

The SplitYamlProvider itself now requires a directory matching the
zone name under its directory to contain all YAML files. This doesn't
actually change the intended usage at all, just how the configuration
file is laid out.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Note that you can't specify a Host header for these which I believe will
complicate the ability to use this. Figuring that out will have to wait
until I or someone else has a use case for these...

This will ensure that deletes come before creates which are before upserts and
that records that uses aliases always come after their target (though implicitly
based on sorting types and not explicitly by looking at them.)

Route53 allows to monitor latency information on the dashboard
and using CloudWatch. While that is a nice to have function,
it is not necessary for a DNS failover scenario and increases
Route 53 costs.
To maintain backward compatibility, the default for this option
when ommited is true.