Use New Install within their own template

It used to be a partial inside #index, but having their own page
yields some extra benefits:

- Performance: Move logic from the view to the controller
  - Theres' no need to go extra steps inside the :index view
- UI: Remove the extra 'Upcoming Conferences' when the system needs
  to start the flow of the creation of the first user

app/views/conferences/index.html.haml

@@ -18,8 +18,6 @@
     #antiquated.collapse
       - @antiquated.each do |conference|
         = render '/conferences/conference_details', conference: conference
-  - if @antiquated.empty? && @current.empty? && User.empty?
-    = render partial: 'new_install'
 
 -content_for :script_body do
   :javascript