3.3.0

• We now use PSR-4 for the directory structure. This means that everything
  that was used to be in the lib/Sabre/VObject directory is now moved to
  lib/. If you use composer to load this library, you shouldn't have to do
  anything about that though.
• VEVENT now get populated with a DTSTAMP and UID property by default.
• BC Break: Removed the 'includes.php' file. Use composer instead.
• #103: Added support for processing [iTip][iTip] messages. This allows a user
  to parse incoming iTip messages and apply the result on existing calendars,
  or automatically generate invites/replies/cancellations based on changes that
  a user made on objects.
• #75, #58, #18: Fixes related to overriding the first event in recurrences.
• Added: VCalendar::getBaseComponent to find the 'master' component in a
  calendar.
• #51: Support for iterating RDATE properties.
• Fixed: Issue #101: RecurrenceIterator::nextMonthly() shows events that are
  excluded events with wrong time