Investigate using revisions for latest edits widget on homepage

[mattheu]

Currently we have some custom HTML, but I think actually just displaying recent revisions would be good.

One reason I think revisions might be nice, is that on a 'latest revisions' archive page we could display the diff of the changes.

One downside is that we would probably get multiple revisions of the same post as often people do 3/4 at once. Perhaps we could do some work to restrict to one per post?