CONTRIBUTION - Recurrent coupons

[neuville11]

Hello @fnando , I have an idea for a contribution to your coupons gem and it is about recurrent coupons, for instance:
one coupon with code HAPPY-HOUR will be redeemable from August 24th to September 28th but it only can be redeemed on Monday, Wednesday and Friday and from 1:00PM to 2:00PM and we can make follow the other restrictions like only 100 global redeems and 3 redeems per user, etc.
We can choose if we want recurrent coupons or normal ones, if the admin doesn't select specific days by default all days are redeemable. (we can choose to be valid during those dates but only in some specific hours, like "all December from 1:00PM to 2:00PM is happy hour")
What do you think about it? We are two guys who want to contribute to open source, we'll be very happy for helping.
Greetings