[Rivet] rivet-mkhtml output requires network access

[David Grellscheid]

Hi all,

we've noticed at the MCnet school that rivet-mkhtml output is not 
useable without network access.  It requires access to the mathjax CDN 
to be available, otherwise browsers hang for up to a minute while that 
access request times out.

At minimum, we need a flag to control that inclusion of the mathjax 
<script> tag in the output.


Secondary to that, the script link should point to Mathjax' https:// 
version.

Thanks,

   David