Added ammount info 

Cannot add ammount off data to stripe coupon: https://stripe.com/docs/api#coupons

{
  "id": "3aad47aaa913405884785e8ae475c886",
  "percent_off": 10,
  "amount_off": null,
  "currency": "usd",
  "object": "coupon",
  "livemode": false,
  "duration": "once",
  "redeem_by": null,
  "max_redemptions": null,
  "times_redeemed": 0,
  "duration_in_months": null
}