rename directory as chapters for simplicity, delete prior copies following move

BookChapters/README.md

-## Book Chapters, Hamming Learning to Learn
-
-These chapters match the final copy (with proofreading markups) sent to the
-publishing company prior to publication.  The publisher applied proper book
-layouts and also replaced hand-drawn line art with matching figures that were
-produced by a professional artist.
-
-Dr. Hamming gave permission for these chapters to get scanned and shared for
-students taking the course who needed the book.  The original versions are in
-the [scans](./scans/) subdirectory.  Updated versions in this directory have been
-produced using [Optical Character Recognition (OCR)](https://en.wikipedia.org/wiki/Optical_character_recognition) 
-via Adobe Acrobat 11 in order to facilitate search.