testing_html - fixing syntax plus editorial

- The syntax highlighting wa snot working correctly, leaving extraneous
  'shell' string in the page.
- Updated localhost to be a link for convenience.
- Since this page is linked from and provided in non-Spice-specific
  places. Toned down the mentions of spice so that the transition is
  not as jarring.

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