Clean up activity.show template, better counts

app/controllers/activities_controller.rb

   # GET /activities/1
   # GET /activities/1.json
   def show
+    @participants = @activity.participants
+      .joins(:person)
+      .order(attending: :desc)
+      .order('people.first_name ASC')
+    @counts = @activity.state_counts
+    @num_participants = @counts.values.sum
   end
 
   # GET /activities/new

app/views/activities/show.html.erb

   <li>Deadline: <%= @activity.deadline %></li>
 </ul>
 
-<h2>Participants (<%= @activity.participants.count %> <%= render partial: "state_counts", locals: {counts:@activity.state_counts}%>)</h2>
+<h2>
+  <%= @num_participants %> participants
+  <%= render partial: "state_counts", locals: {counts:@counts}%>
+</h2>
 <table class="table table-bordered">
-  <% @activity.participants.each do |p| %>
+  <% @participants.each do |p| %>
     <tr class="<%= p.row_class %>" data-person-id="<%= p.person.id %>" data-activity-id="<%= @activity.id %>">
       <td>
         <%= p.person.full_name %>