Update render snippets

They weren't working for me on rails 4+, and also creates the `<%= %>` tags to match [lt snippet](https://github.com/joseramonc/language-ruby-on-rails/blob/f490fbafc1dcdc8f91368e0859f0c21d31099c80/snippets/language-ruby-on-rails.cson#L536) that also create the tags