This is the directory which holds code to generate figures.  The layout is as
follows:

The chapter directories should be called 
 chapter1/
 chapter2/
 chapter3/
etc.

Inside each chapter directory are plotting scripts, which must be of the form

 fig_*.py

The `*` should be a concise & unique descriptor of the file (it will be used
as the image file name).  Each chapter should also have a file called
`contents.txt` in which each line is the name of a file in the directory.
Comments are marked with a #.  This will control the order that the figures
are created on the page.

Additionally, each directory can have a header file `header.rst` which gives
information about the chapter.  If this does not exist, then a basic header
will be created.

Summary:
to add a new figure:
 create a script called chapter*/fig_*.py, where the *'s are suitably replaced
 in the contents.txt file of the directory, add `fig_*py` to the list in the
 appropriate place.