Added redeemable_on field to couponable_coupons. Changed unique index on code and valid_duration to also encompass redeemable_on.
Updated version to 1.1.0 for addition of redeemable_on field to couponable_coupons
Merge pull request #9 from barkbox/redeemable_on

Couponable::Coupon.redeemable_on