Use correct OS name
Use correct OS name

It is called "OS X".

http://www.theverge.com/2012/2/16/2802281/apple-officially-renames-mac-os-x-to-os-x-drops-the-mac
albfan/cpp-coveralls,albfan/cpp-coveralls,eddyxu/cpp-coveralls,eddyxu/cpp-coveralls