The pin expiry option is ignored in the Verify request

[panyushov]

Setting pin expiry to 60 seconds has no effect. SMS received after the API call states that the pin will expire after 5 minutes (default value).

Example:

	opts := vonage.VerifyOpts{
		PinExpiry:  60,
	}
	response, errResp, err := verifyClient.Request(
		phoneNumber,
		"TestBrand",
		opts,
	)