Don't use addNote() when calling HighrisePerson::getNotes()

Calling HighrisePerson->addNote() causes the note to be saved back to Highrise. This is 1) just plain wrong, and 2) erroneously throws an access exception when you're trying to (erroneously) update someone else's note.

@brycied00d made this change here: https://github.com/brycied00d/Highrise-PHP-Api/commit/06ecc6b5305c5a7e589e8b99b55a189d46039f23