Update README.md

Author: Robert Gummesson

README.md

@@ -3,7 +3,7 @@ Build Time Analyzer for Xcode
 
 ## Overview
 
-Build Time Analyzer is an OS X app that shows you a break down of Swift build times. See [this post]( https://medium.com/p/fc92cdd91e31) and [this post](https://medium.com/p/37b0a7514cbe) on Medium for context. 
+Build Time Analyzer is a macOS app that shows you a break down of Swift build times. See [this post]( https://medium.com/p/fc92cdd91e31) and [this post](https://medium.com/p/37b0a7514cbe) on Medium for context. 
 
 ## Usage