def add_business_days(date, delta)
      date = roll_forward(date)
      delta.times do
        begin
          date += day_interval_for(date)
        end until business_day?(date)
      end
      date
    end
def add_business_days(date, delta)
      date = roll_forward(date)
      delta.times do
        begin
          date += day_interval_for(date)
        end until business_day?(date)
      end
      date
    end
Add a number of business days to a date. If a non-business day is given,
 counting will start from the next business day. So,
   monday + 1 = tuesday
   friday + 1 = monday
   sunday + 1 = tuesday