code: public Attendee addAttendee(String email) {
  		Attendee prop = new Attendee(null, email, null);
  		addAttendee(prop);
  		return prop;
  	}
docs: Adds a person who is involved in the to-do task.
  @param email the attendee's email address
  @return the property that was created
  @see <a href="http://tools.ietf.org/html/rfc5545#page-107">RFC 5545
  p.107-9</a>
  @see <a href="http://tools.ietf.org/html/rfc2445#page-102">RFC 2445
  p.102-4</a>
  @see <a href="http://www.imc.org/pdi/vcal-10.doc">vCal 1.0 p.25-7</a>