Fix c&p mistake in README
Fix c&p mistake in README

Referred to Rails 3 example twice

lintangarief/rack-cors,contingencyplan/rack-cors,cyu/rack-cors,lintangarief/rack-cors,kagemusha/rack-cors,MurgaNikolay/rack-cors,rigoleto/rack-cors,ahills/rack-cors,hswolf/rack-cors,ahills/rack-cors,contingencyplan/rack-cors,rigoleto/rack-cors,ahills/rack-cors,hswolf/rack-cors,lintangarief/rack-cors,kagemusha/rack-cors,cyu/rack-cors,contingencyplan/rack-cors,hswolf/rack-cors,kagemusha/rack-cors,rigoleto/rack-cors,MurgaNikolay/rack-cors,cyu/rack-cors,MurgaNikolay/rack-cors