Rename demo engine to enchant.

diff --git a/engine/demo/Makefile b/engine/enchant/Makefile
similarity index 100%
rename from engine/demo/Makefile
rename to engine/enchant/Makefile

diff --git a/engine/demo/engine.py b/engine/enchant/engine.py
similarity index 100%
rename from engine/demo/engine.py
rename to engine/enchant/engine.py

diff --git a/engine/demo/factory.py b/engine/enchant/factory.py
similarity index 100%
rename from engine/demo/factory.py
rename to engine/enchant/factory.py

diff --git a/engine/demo/main.py b/engine/enchant/main.py
similarity index 100%
rename from engine/demo/main.py
rename to engine/enchant/main.py