Add markdown extension to README so github can render it more nicely
Keep a link to the standard README file too.
foreach(dir
Art
Bamboo
Bath
Blox
Brick
Cake
Cave
Castle
Cheese
Christmas
City
Compost
CrazyMission
Deepspace
Desert
EarthRise
Eyes
Freeway
Fruit
Golf
Halloween
Hell
Hoggywood
Island
Jungle
Nature
Olympics
Planes
Sheep
Snow
Stage
Underwater
)
add_subdirectory(${dir})
endforeach(dir)