Fix issues with urls in HITS reference docs

[LorentzFactor]

This is a small PR to address a couple of issues I found in the references section of the HITS algorithm documentation.

1. The link for the first reference was broken. I've updated it to point to a live webpage with a pdf of the paper.
2. The link for the second reference was not being rendered by sphinx as a url. I reordered it with the doi information to get sphinx to recognize it as a link.
3. Lastly, I switch both urls to use https.

[dschult]

Nice !!
Thanks very much!!
:)