This fixes failing tests when the timezone is different than utc

There were several problems:
* Time.now returns the systems time, not the users time
* fixtures do not translate dates from timezone to utc, but stores the
  date verbatim
* calling a controller will set the timezone to the preference of the
  current_user. So it could be changed while you do not realize this. I
  fixed the failing test, but problems could be elsewhere

lib/todo_from_recurring_todo.rb

@@ -27,7 +27,7 @@ class TodoFromRecurringTodo
   end
 
   def end_date
-    todo.due ? todo.due : todo.show_from
+    todo.due || todo.show_from
   end
 
   def attributes