Readme documents browser support
Pixels value object (non-diffable)
Pixels.plus()
Pixels.compare()
Pixels.diff()
Position may be constructed from number or Pixels
Size may be constructed from number or Pixels
Position.toPixels() and Size.toPixels()
Position.plus(): can take Size instance
RelativePosition may be constructed from number or Size
RelativePosition is constructed from number, but uses Size internally
RelativePosition may be relative to ElementSize
RelativePosition may be relative to a RelativeSize
ElementEdge.plus() and .minus() can take an ElementSize
INTEGRATE: Can add ElementSize to ElementEdge

* dev:
  ElementEdge.plus() and .minus() can take an ElementSize
  RelativePosition may be relative to a RelativeSize
  RelativePosition may be relative to ElementSize
  RelativePosition is constructed from number, but uses Size internally
  RelativePosition may be constructed from number or Size
  Position.plus(): can take Size instance
  Position.toPixels() and Size.toPixels()
  Size may be constructed from number or Pixels
  Position may be constructed from number or Pixels
  Pixels.diff()
  Pixels.compare()
  Pixels.plus()
  Pixels value object (non-diffable)
  Readme documents browser support