Update index.md
Update index.md

Replace OS X with macOS
dotfiles/dotfiles.github.com,dotfiles/dotfiles.github.com,unixorn/dotfiles.github.com,dotfiles/dotfiles.github.com,dotfiles/dotfiles.github.com,unixorn/dotfiles.github.com,unixorn/dotfiles.github.com,dotfiles/dotfiles.github.com,unixorn/dotfiles.github.com,unixorn/dotfiles.github.com