Added operating_system.rb to provide more user frindly message when DK is not available.
Added operating_system.rb to provide more user frindly message when DK is not available.

shirosaki/rubyinstaller,leonhooijer/rubyinstaller,jaym/rubyinstaller,shirosaki/rubyinstaller,oneclick/rubyinstaller,zorosteven/rubyinstaller,oneclick/rubyinstaller,suvarnaraju/rubyinstaller,jahanzaibbahadur/rubyinstaller,suvarnaraju/rubyinstaller,suvarnaraju/rubyinstaller,vemmaverve/rubyinstaller,Rugbyman21/rubyinstaller,auyaauya/rubyinstaller,vemmaverve/rubyinstaller,vemmaverve/rubyinstaller,haonaturel/rubyinstaller,modulexcite/rubyinstaller,zorosteven/rubyinstaller,haonaturel/rubyinstaller,haonaturel/rubyinstaller,jahanzaibbahadur/rubyinstaller,jahanzaibbahadur/rubyinstaller,shirosaki/rubyinstaller,modulexcite/rubyinstaller,Rugbyman21/rubyinstaller,auyaauya/rubyinstaller,jaym/rubyinstaller,dreamauya/rubyinstaller,leonhooijer/rubyinstaller,zorosteven/rubyinstaller,oneclick/rubyinstaller,Rugbyman21/rubyinstaller,jaym/rubyinstaller,auyaauya/rubyinstaller,dreamauya/rubyinstaller,leonhooijer/rubyinstaller,dreamauya/rubyinstaller,modulexcite/rubyinstaller