Added CalendarRoot for forward compatbility.
Bumped version.
Using class_alias instead.
Ensuring that the sync-token field gets initialized with a value.
Merge branch '2.0' into 2.1

Conflicts:
	ChangeLog.md
	lib/CalDAV/CalendarRoot.php
	lib/DAV/Version.php
Ensuring that the sync-token field gets initialized with a value.
Merge branch '2.0' of github.com:fruux/sabre-dav into 2.0
Merge branch '2.0' into 2.1