Make sure to scope followed threads by course.

api/notifications_and_subscriptions.rb

@@ -3,7 +3,7 @@ get "#{APIPREFIX}/users/:user_id/notifications" do |user_id|
 end
 
 get "#{APIPREFIX}/users/:user_id/subscribed_threads" do |user_id|
-  handle_threads_query(user.subscribed_threads)
+  handle_threads_query(user.subscribed_threads.where(:course_id=>params[:course_id]))
 end
 
 post "#{APIPREFIX}/users/:user_id/subscriptions" do |user_id|