Octodns-cloudflare

* TtlToProxy processor added to enable the proxied flag based on a sentinel
ttl value. Useful when the source is not YamlProvider
* Add support for comments & tags via octodns.cloudflare.comment|tags
* ProxyCNAME processor added to aid in supporting Cloudflare prixed values
with non-Cloudflare DNS providers by directing them to the relevant
.cdn.cloudflare.net. CNAME / ALIAS value.

* Support for Provider.list_zones to enable dynamic zone config when operating
as a source
* Support for auto-ttl without proxied as records can be configured that way,
see auto-ttl in README.md for more info
* Fix bug in handling of empty strings/content on TXT records
* Make the minumum supported TTL configurable.

* SPF records can no longer be created,
https://github.com/octodns/octodns-cloudflare/issues/28
* NAPTR and SSHFP support added
* All HTTP requests include a meaningful user-agent.
* AccountID filter support
* API token auth method/doc

* Added support for TLSA record type
* Switched to pytest and updated everything to latest template setup

Nothworthy Changes

* Initial extraction of CloudflareProvider from octoDNS core

Stuff

Nothing