update README for typical DevKit build instructions
update README for typical DevKit build instructions

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