Given a month as an integer from 1 to 12, return to which quarter of the year it belongs as an integer number.
For example: month 2 (February), is part of the first quarter; month 6 (June), is part of the second quarter; and month 11 (November), is part of the fourth quarter.
Constraint:
- 1 <= month <= 12
def quarter_of(month)
(month/3.0).ceil
end