Rename README.markdown to README.md
Move teardrop.scad to shapes/teardrop.scad
Split test_teardrop() out to new file demos/teardrop_demo.scad
Remove echo() statement from general/constants.scad
Create echo() statements in new file demos/constants_demo.scad
Move polyholes.scad to shapes/polyhole.scad
Move function test_polyhole() to new file demos/polyhole_demo.scad