Merge pull request killbill#619 from killbill/aviate-coupons

coupon: Add MaxUse attributes

Author: sbrossie

userguide/aviate/aviate-coupons.adoc

@@ -16,6 +16,7 @@ A coupon in Aviate consists of the following attributes:
 
 * `Redemption code`: A unique code that customers can use to apply the discount.
 * `Reusability`: Whether the coupon can be applied multiple times by the same customer.
+* `MaxUse`: Maximum number of times a coupon can be redeemed.
 * `Discount type`: The discount calculation method:
 ** `Fixed`: Applies a fixed monetary amount.
 ** `Percentage`: Applies a percentage-based discount.