Zip payment method not returning in API #101

Expected behavior

Zip should be returned as a payment method in the PaymentMethods API resource when it is enabled.

Actual behavior

Zip is not returned as a payment method.

Steps to reproduce behavior

1. Enable Zip as a payment method in the store
2. Connect to API and run api.PaymentMethods.all()
3. Zip is not returned as one of the enabled payment methods