chronology port from squeak 3.7

Hello all.

I've started to port chronology package from Squeak 3.7. However, in the
last weeks I didn't have the time to finish it as I would want, and I also
think I won't have the time to do it for some more weeks.
Anyway, I've posted a first version in
http://www.bokonon.com.ar/chronology/chronology.html in case anyone is
interested.
Please, do not install the package in your working image before making a
backup first.
Please, try to ignore all my grammar and orthographic errors :)

Best regards.
Martin.