3.1.3

• Set minimum libxml version to 2.7.0 in composer.json.
• #805: It wasn't possible to create calendars that hold events, journals and
  todos using MySQL, because the components column was 1 byte too small.
• The zip release ships with sabre/vobject 4.1.0,
  sabre/http 4.2.1, sabre/event 3.0.0,
  sabre/uri 1.1.0 and sabre/xml 1.4.1.