Update README.md

Updated to N4073.
Merge branch 'N3888-successor' of https://github.com/mikebmcl/N3888_RefImpl.git
Revert "Renamed surface::push_group_with_content to surface::push_group. Renamed surface::copy_clip_rectangle_list to surface::get_clip_rectangles. Added path_data validation code to path class constructor."

This reverts commit 42a1981dba373fb956d5d64140fe2008be13de82.
Merge pull request #28 from mikebmcl/master

Making branch current with the v.4073 release