added testGetContactsWithIllegalId to test that putting in an id that doesn't exist throws an exception
Wrote testGetContactsWithIllegalName to check that getContacts with a nonexistant name throws IllegalArgumentException.
Commented out testGetContactsWithNullArg, as getContacts(null) is an ambiguous reference.
Modified getContact(String name) to throw a NullPointerException if argument is null.
Accidentally extracted constant from exception. Undid change.
Wrote new test for addNewPastMeeting().
Added a getter for internal pastMeetingList for debugging purposes - will remove once all other methods implemented.
Wrote addNewPastMeeting. Instantiated internal pastMeetingList in constructor.