Some sections jumped from level 2 to level 4, for example.
Also played around with generating book to HTML. I like it, but
it needs some work. The Calico table of content generator cannot
deal with different headers with the same name, for example.
I want to go to HTML so I can use Bokeh to have interactive plots.
But that means no more PDF, because Bokeh will not export to
PDF.
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