testing_html - fixing syntax plus editorial

- The syntax highlighting was not working correctly, leaving extraneous
  'shell' strings in the page.
- Updated localhost URL to a link for convenience.
- Toned down mentionds of Spice, since this page is linked from and
  provided in non-Spice-specific places. Hopefully, the transition is
  not as jarring.

As is my wont, this also includes other editorial changes since I was
here and doing edits, anyway.