code: public Database asynchronous(final Scheduler nonTransactionalScheduler) {
          return asynchronous(new Func0<Scheduler>() {
              @Override
              public Scheduler call() {
                  return nonTransactionalScheduler;
              }
          });
      }
docs: Returns a Database based on the current Database except all
  non-transactional queries run on the given scheduler.
  
  @return new Database instance