added debugging framework, including multiple debug levels (only 0-2

currently used)

bug fix (workaround) for PHP/SimplePie leaking memory
bug fix for google xml not giving correct results sortorder=ascenting
was needed.
2500 events are no longer downloaded and pared down - it only requests
as many events as num_events. If you have multiple interleaved
calendars, this means num_events * N, where N is the number of
calendars, but it will take only the first num_events events.