cmd/present: adjust article presentation

* Give the article title a larger, heavier font than any heading.
  It was strange that the title was 20px regular while the
  h1 section headings were 24px.

* Move the author attribution to the top of the page.
  Author at the bottom, like a signature, may make sense for blog posts,
  but I think it makes less sense for articles.

* Fix the spacing around author lines. Each author line is a <p>
  and the intent seemed to be to cut the vertical space between them
  but that wasn't working.

* Give the table of contents a title, to make clearer what it is.
  Do not show table of contents in printouts.

Change-Id: Iee940ca7697015281fc057750f5db56f70393836
Reviewed-on: https://go-review.googlesource.com/33578
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
2 files changed