Increase default page width

[artob]

If I may, I would suggest that the default template's body width could perhaps be slightly increased. Right now, e.g. http://markdoc.org/ looks really (too) tiny on a decent-sized screen. The http://unlicense.org/ template, by contrast, looks rather more readable; I don't recall whether I adjusted that myself, or whether the default template back in the day used to be wider.