* Refactor tests out of module for certbot-dns-cloudflare
* Refactor tests out of module for certbot-dns-cloudxns
* Refactor tests out of module for certbot-dns-digitalocean
* Refactor tests out of module for certbot-dns-dnsimple
* Refactor tests out of module for certbot-dns-dnsmadeeasy
* Refactor tests out of module for certbot-dns-gehirn
* Refactor tests out of module for certbot-dns-google
* Refactor tests out of module for certbot-dns-linode
* Refactor tests out of module for certbot-dns-luadns
* Refactor tests out of module for certbot-dns-nsone
* Refactor tests out of module for certbot-dns-ovh
* Refactor tests out of module for certbot-dns-rfc2136
* Refactor tests out of module for certbot-dns-sakuracloud
* Refactor tests out of module for certbot-dns-route53
* Move certbot-dns-google testdata/ under tests/
* Use pytest for dns plugins
* Exclude pycache and .py[cod]
