Thinking at_xpath is better in these places
Dot prefix helps with our xpath

Especially when we start handling sub-parts like the PaymentMethod
within an AddPaymentMethod transaction.
Make it easier to write unit tests

Now allowing an ENV var to be used when running a remote test to show us
the actual response from Spreedly in the console.  This allows us to
easily stub things out in the unit tests.
Move more testing from remote to unit

Also making remote tests less dependent on the state of the server
account since the find_payment_method test is now putting a payment
method up there first.