Octodns

* EtcHostsProvider implementation to create static/emergency best effort
content that can be used in /etc/hosts to resolve things.
* Add lenient support to Zone.add_record, allows populate from providers that
have allowed/created invalid data and situations where a sub-zone is being
extracted from a parent, but the records still exist in the remote provider.
* AXFR source support added
* google-cloud-dns requirement instead of general package

NOTICE

Using this version on existing records with `geo` will result in
recreating all health checks. This process has been tested pretty thoroughly to
try and ensure a seamless upgrade without any traffic shifting around. It's
probably best to take extra care when updating and to try and make sure that
all health checks are passing before the first sync with `--doit`. See
[67](https://github.com/octodns/octodns/pull/67) for more information.

* Major update to geo healthchecks to allow configuring host (header), path,
protocol, and port [67](https://github.com/octodns/octodns/pull/67)
* SSHFP algorithm type 4
* NS1 and DNSimple support skipping unsupported record types
* Revert back to old style setup.py & requirements.txt, setup.cfg was
causing too much pita

* Way way way too much to list out here, shouldn't have waited so long
* Initial NS1 geo support
* Major reworking of `CloudflareProvider`'s update process, was only partially
functional before, also ignore proxied records
* Fixes and improvements to better support non-ascii records and zones
* Plans indicate when Zones are going to be created
* Fix for `GoogleCloudProvider` handling of ; escapes
* Skip Alias recordsets for Route53 (unsupported concept/type)
* Make sure that Record geo values are sorted to prevent false diffs that can
never be fixed
* `DynProvider` fix to safely roll rulesets, things could end up on rules
without a pool and/or hitting the default rule previously.

* Added support for "chunking" TXT records where individual values were larger
than 255 chars. This is common with DKIM records involving multiple
providers.
* Added `GoogleCloudProvider`
* Configurable `UnsafePlan` thresholds to allow modification of how many
updates/deletes are allowed before a plan is declared dangerous.
* Manager.dump bug fix around empty zones.
* Prefer use of `.` over `source` in shell scripts
* `DynProvider` warns when it ignores unrecognized traffic directors.

Adds an OVH provider.

Misc fixes and improvements.

* Azure TXT record fix
* PowerDNS api support for https
* Configurable Route53 max retries and max-attempts
* Improved key ordering error message