Balance: Wrong type for new InstantAvailable field

[jheth]

This change introduced a serialization issue:

stripe-go/balance.go

Line 40 in fb2310e

InstantAvailable *BalanceDetails `json:"instant_available"`

[ERROR] Couldn't deserialize JSON (response status: 200, body sample: '{\n "object": "balance",\n "available": [\n {\n "amount": 118300,\n "currency": "usd",\n "source_types": {\n "card": 118300\n }\n }\n ],\n "instant_available": [\n {\n "amount": 118300,\n "currency": "usd",\n "source_types": {\n "card": 118300\n }\n }\n ],\n "livemode": false,\n "pending": [\n {\n "amount": 0,\n "currency": "usd",\n "source_types": {\n "card": 0\n }\n }\n ]\n}\n'): json: cannot unmarshal array into Go struct field Balance.instant_available of type stripe.BalanceDetails

It needs to be[]*Amount instead of *BalanceDetails

InstantAvailable []*Amount               `json:"instant_available"`