Diviner: improve links, book index, and atom view
Summary: Ref T988. Minor improvements to diviner: link stuff to a valid endpoint which actually works; fix group names on the book index; improve the topics index for atom views.
Test Plan: Clicked links in an article, viewed book index, viewed an article with long headers.
Reviewers: btrahan, chad
Reviewed By: chad
Maniphest Tasks: T988
Differential Revision: https://secure.phabricator.com/D6598