move doc files to docs/

diff --git a/images/slideshow.png b/docs/images/slideshow.png
similarity index 100%
rename from images/slideshow.png
rename to docs/images/slideshow.png

diff --git a/images/tutorial1-1.png b/docs/images/tutorial1-1.png
similarity index 100%
rename from images/tutorial1-1.png
rename to docs/images/tutorial1-1.png

diff --git a/images/tutorial1-2.png b/docs/images/tutorial1-2.png
similarity index 100%
rename from images/tutorial1-2.png
rename to docs/images/tutorial1-2.png

diff --git a/introduction.lisp b/docs/introduction.lisp
similarity index 100%
rename from introduction.lisp
rename to docs/introduction.lisp

diff --git a/manual.pdf b/docs/manual.pdf
similarity index 100%
rename from manual.pdf
rename to docs/manual.pdf

diff --git a/pbook.py b/docs/pbook.py
similarity index 100%
rename from pbook.py
rename to docs/pbook.py

diff --git a/reference.lisp b/docs/reference.lisp
similarity index 100%
rename from reference.lisp
rename to docs/reference.lisp

diff --git a/reference.pdf b/docs/reference.pdf
similarity index 100%
rename from reference.pdf
rename to docs/reference.pdf

diff --git a/tutorial.lisp b/docs/tutorial.lisp
similarity index 100%
rename from tutorial.lisp
rename to docs/tutorial.lisp