Update README.md
Merge branch 'HEAD' of https://github.com/magic3dcn/magic3d.git into develop
Merge branch 'develop' of https://github.com/magic3dcn/magic3d.git into develop
update
Merge branch 'develop' of https://github.com/magic3dcn/magic3d.git into develop
Add precompile header to enhance the compile speed.