Add Route 53 auto-updating

[cfairweather]

If a user provides:

• an env AWS_KEY
• an env AWS_SECRET
• and their Route 53 has a zone associated with the root of the domain(s) provided in LE_DOMAIN

then automatically update A (and CNAME?) records to match the current container.

Considerations:

• Parsing tlds
• The apex of a domain cannot have a CNAME

[cfairweather]

More considerations:

• Check public IP (in a secure manner?)
• Only set A record with detected public IP