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/_new_install.html.haml

@@ -1,21 +0,0 @@
-.row
-  .col-md-12
-    .well
-      %h1
-        Welcome to your new
-        = link_to('https://osem.io') do
-          Open Source Event Manager
-        installation!
-      %p
-        The first user to
-        - if ENV['OSEM_ICHAIN_ENABLED'] == 'true'
-          = link_to(new_ichain_registration_path('user')) do
-            sign up
-        - else
-          = link_to(new_registration_path('user')) do
-            sign up
-        will the be administrator of it.
-      %p
-        We hope you enjoy using OSEM, if you have any question don't hesitate to
-        = link_to('http://osem.io/#contact') do
-          contact us!