Moved book generation code into PDF directory

Start of a reorganization of files to make book more browable and to
reduce the size of links to chapters.

pdf/update_pdf.sh

@@ -0,0 +1,8 @@
+#! /bin/bash
+
+git checkout gh-pages
+git checkout master Kalman_and_Bayesian_Filters_in_Python.pdf
+git add Kalman_and_Bayesian_Filters_in_Python.pdf
+git commit -m 'updating PDF'
+git push
+git checkout master