Chapter 3 section 3.6.4.

* [spa:shell] control chat slider state via URI anchor.
Chapter 4 section 4.2.1.

* [spa:application] add modular files.
  * JavaScript for chat.
  * JavaScript for model.
  * JavaScript for utility.
  * Stylesheet for chat.
  * delete layout.html
Chapter 4 section 4.2.2.

* [spa:chat] add spa.chat.