Static pure function interface

Added

• Added TestResult type which is returned from test() and can be checked directly
  for collisions or passed to intersect() to further calculate an intersection
• Added IntersectResult type which is returned from intersect() and can be used
  to calculate collision normals, separation distances, etc
• Added Headbutt.testAndIntersect() function which is a shortcut for testing and
  then calculating the intersection if a collision is found

Changed

• Changed Headbutt interface from interacting with an object with internal state
  to static pure functions (i.e. call Headbutt.test() instead of new Headbutt().test())

Shape Transforms

Added

• Added transformation support to all provided shape classes
• Added tests for most shapes (not lines)
• Added tests for transformed shape collision calculations
• Added API documentation to all public interfaces

Changed

• Changed Shape.origin getter/setter to a single Shape.centre getter
• Changed shape contructors to align with using transforms instead of an initial offset

Normalized Shape API

Added

• Added 3D shapes
• Added 2D shapes
• Added some API documentation

Changed

• Split 2D and 3D into their own packages: headbutt.twod and headbutt.threed
• Changed Shape.centre to Shape.origin

Initial release

• 2D shape collision checking
• 2D shape intersection calculations
• 3D shape collision checking