update Ruby versions in Travis config
update Ruby versions in Travis config

sharpfuryz/inherited_resources,lambda2/inherited_resources,josevalim/inherited_resources,sharpfuryz/inherited_resources,lambda2/inherited_resources,activeadmin/inherited_resources,josevalim/inherited_resources,activeadmin/inherited_resources,activeadmin/inherited_resources,aratak/inherited_resources,josevalim/inherited_resources,aratak/inherited_resources