List users who haven't voted

Closes #3

views/votes_show_open.erb

@@ -66,9 +66,17 @@
 <h2 class="mb-4"><%= _("Participants") + " (#{@vote.ratings.collect { |rating| rating.user }.uniq.count})" %></h2>
 
 <ul class="mb-5">
-<% @vote.ratings.collect { |rating| rating.user }.uniq.sort_by { |user| user.email }.each do |user| %>
-  <li><%= user.email %></li>
-<% end %>
+  <% all_users_sorted.each do |user| %>
+    <li>
+      <% if @vote.ratings.collect { |rating| rating.user }.include?(user) %>
+        <span>
+      <% else %>
+        <span class="text-decoration-line-through">
+      <% end %>
+      <%= user.email %>
+      </span>
+    </li>
+  <% end %>
 </ul>
 
 <% if @vote.users.exists?(current_user.id) and @vote.expire_on.nil? %>