* add transform-class-properties to stage 3, set spec mode to default * update readme with examples; use `buildUndefinedNode()`; change behavior to always define both static and nonstatic class properties regardless of spec/loose mode; update tests
* add transform-class-properties to stage 3, set spec mode to default * update readme with examples; use `buildUndefinedNode()`; change behavior to always define both static and nonstatic class properties regardless of spec/loose mode; update tests