checkpoint; in midst of big re-org.

This is not a 'useful'checkin. I'm heavily reorganizing teh
multivariate chapter (spliltting in two) and I am getting
worried about losing edits.

pdf/build_book

@@ -1,6 +1,6 @@
 #! /bin/bash
 
-echo "merging book..."
+#echo "merging book..."
 python merge_book.py
 
 echo "creating pdf..."