I took a crack at adding pagination to the diff viewer.  The problem I'm trying to solve is that, when the diffs are too big, the browser has trouble displaying them.  There is a typical list of page numbers and previous/next links.  The code is based on the paginator stuff I saw on the Django website.  I also modified the links in the threaded comment view to include the file id as a parameter, so we can flip to the right page.