Decoding to not-nil interface returns error

[fxamacker]

The following code returns error "cbor: cannot unmarshal array into Go value of type interface {}"

s := "hello"
var v interface{} = s
cbor.Unmarshal(data, &v)

Decoder should handle not-nil interface in the same way as nil interface by storing appropraite Go type in the interface value. This behavior should be made consistent with encoding/json.