Move diff pagination into javascript.
The pagination selector is pretty ugly and terrible at this point, and we'll

probably redesign this later, but for now, I'd like to keep it as-is but allow

it to update dynamically so we can load different revisions. This change moves

its rendering into javascript.

Set up a few different revisions with different pagination. Checked that the

pagination selector rendered appropriately in different cases, and that the

different links went to the right pages.