initial commit
change defaults
handle zero case, add documentation
CHANGES: 1.1 release date
headWidth, tailWidth, widths
3D colors, material reflectance

closes #121
simpler angleBetween
Add trig functions using Angle
lenses for polar coordinates

3D: spherical and cylindrical
2D: using the same type classes as cylindrical
allow vector-space-points-0.2
Bump version to 1.1.0.1
Release notes for 1.1.0.1
make R3 strict data like R2
Make Direction a type, not a type class
Add Box
Add Frustum
Wall: remove extra imports
explicit instances for HasPhi, HasR, HasTheta to avoid overlap
make HasR _r lens be the vector magnitude

This definition works in all vector spaces, and is probably more often
useful.  The cylindrical r is easy to refer to as cylindrical._1; it
just happens that it was the case that motivated me to write these lenses.
move avgScale to core