Link to Yosemite marketing page

Author: Dan Croak

README.md

@@ -9,7 +9,7 @@ Requirements
 We support:
 
 * [OS X Mavericks (10.9)](https://itunes.apple.com/us/app/os-x-mavericks/id675248567)
-* OS X Yosemite (10.10)
+* [OS X Yosemite (10.10)](https://www.apple.com/osx/)
 
 Older versions may work but aren't regularly tested. Bug reports for older
 versions are welcome.