Get rid of user activites table and replace it with redis

• Gets rid of the user activities table
• Switch from postgreSQL to Redis

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/1158

spec/controllers/sessions_controller_spec.rb

@@ -16,7 +16,9 @@
         end
       end
 
-      context 'when using valid password' do
+      context 'when using valid password', :redis do
+        include UserActivitiesHelpers
+
         let(:user) { create(:user) }
 
         it 'authenticates user correctly' do
@@ -34,7 +36,7 @@
         it 'updates the user activity' do
           expect do
             post(:create, user: { login: user.username, password: user.password })
-          end.to change { user.reload.last_activity_at }.from(nil)
+          end.to change { user_score }.from(0)
         end
       end
     end