Clean up config.toml

[AngeloStavrow]

Right now there's a bit too much redundancy between config.toml and the page front-matter, like author/AuthorName parameters. I removed the .Site.Params.AuthorName parameter in a9cb556, but we should better define site and post authors.

To do:

• Default to .Params.Author but fallback to .Site.Author (don't forget footer.html!)
• Remove .Site.Params.CopyrightOwner for .Site.Copyright

[AngeloStavrow]

Oddly, I can't get .Site.Author as configured in the example Hugo site's config.toml file to render.

[AngeloStavrow]

We can work around this with a .Site.Params.Author in the config.toml file; we'll have to specify this in the README docs. Additionally, since we're using variable overwrites, we'll need to specify a minimum version for Hugo of 0.48.