* certbot-dns-linode : Added support for linode version 4 tokens
* certbot-dns-linode : Added credentials ini option to override automatic api version detection
* certbot-dns-linode : Added clearer messages and documentation based on review
* certbot-dns-linode : Added check for empty 'linode_version' config instead of missing
* certbot-dns-linode : Fix rebase on master
* certbot-dns-linode : Updated local-oldest-requirements.txt
* Updated CHANGELOG to indicate Linode v4 API key support
