Update README.md to mention CMake
Update README.md to mention CMake

Link to wiki for building with cmake
hostilefork/rebol,rgchris/ren-c,hostilefork/rebol,giuliolunati/ren-c,giuliolunati/ren-c,draegtun/ren-c,rgchris/ren-c,kealist/ren-c,draegtun/ren-c,kealist/ren-c,hostilefork/rebol,draegtun/ren-c,codebybrett/ren-c,kealist/ren-c,codebybrett/ren-c,hostilefork/rebol,kealist/ren-c,giuliolunati/ren-c,hostilefork/rebol,draegtun/ren-c,draegtun/ren-c,hostilefork/rebol,codebybrett/ren-c,codebybrett/ren-c,rgchris/ren-c,codebybrett/ren-c,kealist/ren-c,giuliolunati/ren-c,kealist/ren-c,codebybrett/ren-c,rgchris/ren-c,draegtun/ren-c,giuliolunati/ren-c,rgchris/ren-c