README: use double quotes in all ruby examples
README: use double quotes in all ruby examples

zuazo/chef-handler-sns,onddo/chef-handler-sns,mixpanel-platform/chef-handler-sns,mixpanel-platform/chef-handler-sns,mevic/chef-handler-sns,onddo/chef-handler-sns,zuazo/chef-handler-sns,mevic/chef-handler-sns