Add support for viewing past activities

app/controllers/activities_controller.rb

   # GET /groups/:id/activities
   # GET /activities.json
   def index
-    @activities = @group.activities
-      .where('start > ?', Time.now)
-      .order(start: :asc)
-      .paginate(page: params[:page], per_page: 25)
+    if params[:past]
+      @activities = @group.activities
+        .where('start < ?', Time.now)
+        .order(start: :desc)
+        .paginate(page: params[:page], per_page: 25)
+    else
+      @activities = @group.activities
+        .where('start > ?', Time.now)
+        .order(start: :asc)
+        .paginate(page: params[:page], per_page: 25)
+    end
   end
 
   # GET /activities/1

app/views/activities/index.html.haml

 %h1
-  = t 'activerecord.models.activity.other'
-
-= link_to new_group_activity_path(@group), class: 'btn btn-default pull-right' do
-  %i.fa.fa-plus
-  = t 'activities.new'
+  - if params[:past]
+    = t 'activities.past'
+  - else
+    = t 'activities.upcoming'
 
 - isleader = @group.leaders.include?(current_person) || current_person.is_admin?
+.btn-group.pull-right
+  - if params[:past]
+    = link_to group_activities_path(@group), class: 'btn btn-default' do
+      %i.fa.fa-history
+      = t 'activities.upcoming'
+  - else
+    = link_to group_activities_path(@group, past: true), class: 'btn btn-default' do
+      %i.fa.fa-history
+      = t 'activities.past'
+  - if isleader
+    = link_to new_group_activity_path(@group), class: 'btn btn-default' do
+      %i.fa.fa-plus
+      = t 'activities.new'
 
 %table.table
   %thead
               %i.fa.fa-pencil
 
 = will_paginate @activities
-

config/locales/activities/en.yml

     mass_import: "Create multiple activities in %{group}"
     mass_imported: "%{count} activities created!"
 
+    upcoming: 'Upcoming activities'
+    past: 'Past activities'
+
     mass_import_explanation: "Download the example file using the link below, fill in the fields (end and deadline are optional), and upload the file using the upload form."
 
     upcoming_yours: "Upcoming activities organized by you"

config/locales/activities/nl.yml

     mass_import: "Meerdere activiteiten aanmaken in %{group}"
     mass_imported: "%{count} activiteiten aangemaakt!"
 
+    upcoming: 'Aankomende activiteiten'
+    past: 'Afgelopen activiteiten'
+
     mass_import_explanation: "Download het voorbeeldbestand via de link hieronder, vul de velden in in het formaat zoals het staat aangegeven (einde en deadline zijn niet verplicht), en upload het via de knop onderaan."
 
     upcoming_yours: "Aankomende activiteiten georganiseerd door jou"