Update README.md

Merge pull request #32 from larskanis/add-11.1

Add MacOSX11.1.sdk

Merge pull request #23 from serjepatoff/master

Added 10.15 SDK (from Command Line Tools for Xcode 11)

Add 10.14 beta 4 SDK

Edit README

Merge pull request #7 from phracker/MacOSX10.11_15A278

Update MacOSX10.11.sdk to 15A278