Added 'Customer' model.
Added 'Customer' view model.
Re-wrote 'Customer' view model using Underscore.js.
Added 'Customer' controller.
Added customer registration (/customer/registration) and customer home
views.

Please note that there are significant changes from the code samples
given in Chapter 17 of the book.  That code was not tested in advance,
unfortunately, and had to be modified to work.  My apologiers to my
readers.