This file would seem to be the source for /contributors, but actually
it's a fallback for /website/content/tmpl/contrib.html.
Add a comment explaining the automatic generation to avoid confusion
for folks attempting to edit the website.
Also rename the template to contributing.html for consistency.
Change-Id: Ic98c494b0cc24292dac8a4a22c751aded87f5b48
Eric Drechsel