Simplify footer copyright info

[nate-double-u]

In terms of copyright, the rules were simplified a little while ago, so that we can (AFAIK), have a clean footer like this one from etcd.io:

Originally posted by @chalin in #58 (comment)

[kapunahelewong]

That's a nice footer. I'd be happy to take this one once #73 is merged.

[chalin]

That's a nice footer. I'd be happy to take this one once #73 is merged.

Thanks. Btw, that footer comes from a Docsy themed site, ... so maybe it makes the most sense to decide on #64 first?