Updates to work with current nginx community cookbook

Disabling the default site can now be handled by setting an attribute.  In the community cookbook `nginx_site` now [assumes a default template](https://github.com/opscode-cookbooks/nginx/blame/master/definitions/nginx_site.rb#L22) of `default-site.erb` whenever it's invoked.  Had to set the template to false so that it skips trying to setup the site and just enables it.