Cut down traffic from embed #2

I wrote Embed #2 to update every 30 seconds or so, but that creates more
traffic than it's worth.
Bump version to 5.6.1
Bump version to 5.6.1-dev
Upgrade to latest Aspen
Bump version to 5.6.2
Bump version to 5.6.2-dev
Note Affero in README
Footer stats link is wrong

Both `/about/stats` and `/about/stats.html` works, I'm not sure what is the correct link to be used.
Merge pull request #457 from iurisilvio/patch-1

Footer stats link is wrong; I'm not sure why the tests are failing but it's not due to this I'll tell ya.