0.5.0

* Record post-contact impulses in buffering-contact-listener.
* Allow vary-user-data to take variadic arguments, like vary-meta.
* Add gravity accessor function.
* Use styler side-effecting function instead of color map in testbed.
* Draw zero-angle line on circles.

0.4.0

* Added chain shape.
* Defined testbed camera with a :center position.
* Implemented mouse wheel zooming.
* Support for gravity scale.
* Added world contact list.
* Removed edge-point function from core, and angle* from vec2d.
* Renamed vec2d/edge-point-from-vertices to vec2d/poly-edge-point.
* New core functions to generate snapshot values of world for drawing.
* Draw in testbed from a scene snapshot value, not direct query.
* Record history of snapshots in testbed, allowing rewind.
* Help text in testbed drawing window, world time, and more commands.

0.3.0

* Initial release.