Squashed commit of the following:

commit fbaa65e5a966781eac71456815c0979fad0716af
Author: Alejandro Baez <alejan.baez@gmail.com>
Date:   Mon Jan 20 16:48:24 2014 -0500

    finished ch13 review

commit 52c79bdef7a5b9b968b9d8f2b42dec6f90cee77a
Author: Alejandro Baez <alejan.baez@gmail.com>
Date:   Sat Jan 18 16:07:41 2014 -0500

    up to ch13.4