I made a separate filterpy.stats module becuase it made
little sense to import filterpy.common for stats
functions. This required a lot of changes in the notebooks
and supporting code.
I made a lot of changes so that each chapter makes clear that
they are all implementing the same basic bayesian algorithm.
This required a lot of editting, and it doesn't make sense to
try to do that atomically, hence this huge check in.
I made a lot of edits, and haven't copy editted anything. i'm
sure I introduced a lot of problems and discontinuities.
Let this check in get away from me. Bunch of small formatting sttuf
in the various chapters, some experimental animations and code, etc.
Not a clearly delineated check in.
