records guest connect/disconnect events.
.max_events -- maximum number of connect/disconnect events kept
.connections -- actual list of events, the most recent ones first
each element is of the form
{object, is_connect, time, site}
object is the particular guest that (dis)connected
is_connect 1 or 0 according as this is a connect or not.
:find(who,when)
=> site name of WHO at the particular time
(or 0 if WHO was not logged in then)
:last(n)
prints a listing of the last n events