Addition or subtraction of a Size with a PointZero should return a Point
Allow a Circle to be created without a center argument

The center property defaults to PointZero
Removed the module-level line and point methods

It was a silly idea
Switched Arc.new to named arguments
Documentation fixes for Circle
Added start and end arguments to Line.new
Added push and last methods to Path
Switched RegularPolygon.new to named parameters
Switched Square to named arguments

This class still needs a lot of work
Fixed some warnings