updating tested distros in readme
updating tested distros in readme

elastera/varnish,elastera/varnish,bitzesty/varnish,rackspace-cookbooks/varnish,yoshiwaan/varnish,KierranM/varnish,jujugrrr/varnish,GannettDigital/chef-varnish,jujugrrr/varnish,gusrc/varnish,gsreynolds/varnish,gsreynolds/varnish,TAKEALOT/varnish,gusrc/varnish,KierranM/varnish,TAKEALOT/varnish,rackspace-cookbooks/varnish,gusrc/varnish,yoshiwaan/varnish,GannettDigital/chef-varnish,rackspace-cookbooks/varnish