feat(apple pay): add support for recurringPaymentRequest, move to options.paymentRequest

[cbarton]

Cleans up the interface for calling into recurly.ApplePay so that the
properties that drift down to the resulting payment request are not
intermixed with the SDK specific parameters.

As a result, deprecates options.requiredShippingContactFields in favor
of reading it off of the paymentRequest.requiredShippingContactFields.

Adds options.recurring that, when provided in combination with
options.total, will create a total that will include a monthly
recurring charge on the payment sheet.

options.paymentRequest will be treated as the source of truth, except
for when options.pricing is provided. This maintains the stance that
Pricing controls the total and lineItems.

Can be will be generated if the total line item is set to paymentTiming='recurring':

const applePay = recurly.ApplePay({
  total: '29.00',
  recurring: true,
});

OR specified as the recurringPaymentRequest option:

const total: ApplePayLineItem = {
  label: 'My Subscription',
  paymentTiming: 'recurring',
  amount: '29.00',
  recurringPaymentIntervalUnit: 'month',
  recurringPaymentIntervalCount: 1,
  recurringPaymentStartDate: new Date(),
};

const applePay = recurly.ApplePay({
  paymentRequest: {
    total,
    recurringPaymentRequest: {
      paymentDescription: 'A recurring subscription',
      regularBilling: total,
      billingAgreement: 'Will recur forever',
    }
  }
});

[coveralls]

Coverage: 92.437% (+0.01%) from 92.427% when pulling 1fd0816 on recurring-payment-request into a408657 on master.

[chrissrogers]

The tests here just need an update to comply with the changeset in #802

[chrissrogers]

nit: this being a boolean will prevent it from setting through consistently when the option is provided. The side-effect of this will result in success, since false and undefined are functionally equivalent to the way this option is interpreted.

Simple fix would be to do if ('recurring' in options) /* ... */ or if (typeof options.recurring !== 'undefined')