README.md: Update Mac OS X to macOS

Signed-off-by: Lilis Iskandar <[email protected]>

Author: veeableful

README.md

@@ -27,7 +27,7 @@ On __Arch Linux__, type:
 On __Gentoo__, type:  
 `emerge -av libsdl2 sdl2-{gfx,image,mixer,ttf}`
 
-On __Mac OS X__, install SDL2 via [Homebrew](http://brew.sh) like so:  
+On __macOS__, install SDL2 via [Homebrew](http://brew.sh) like so:  
 `brew install sdl2{,_image,_ttf,_mixer} pkg-config`
 
 On __Windows__,  
@@ -140,7 +140,7 @@ UPDATE: Recent update added a call queue system where you can put thread-sensiti
 __Why can't SDL_mixer seem to play MP3 audio file?__  
 Your installed SDL_mixer probably doesn't support MP3 file.
 
-On __Mac OS X__, this is easy to correct. First remove the faulty mixer: `brew remove sdl2_mixer`, then reinstall it with the MP3 option: `brew install sdl2_mixer --with-flac --with-fluid-synth --with-libmikmod --with-libmodplug --with-smpeg2`. If necessary, check which options you can enable with `brew info sdl2_mixer`.
+On __macOS__, this is easy to correct. First remove the faulty mixer: `brew remove sdl2_mixer`, then reinstall it with the MP3 option: `brew install sdl2_mixer --with-flac --with-fluid-synth --with-libmikmod --with-libmodplug --with-smpeg2`. If necessary, check which options you can enable with `brew info sdl2_mixer`.
 
 On __Other Operating Systems__, you will need to compile smpeg and SDL_mixer from source with the MP3 option enabled. You can find smpeg in the `external` directory of SDL_mixer. Refer to issue [#148](https://github.com/veandco/go-sdl2/issues/148) for instructions.