litle: support wiredump_device

By specifying a wiredump device, such as:

  ActiveMerchant::Billing::LitleGateway.wiredump_device = File.open('/var/tmp/litle.log', 'w')

the device will now be properly passed to the LitleOnline gem for logging.

The LitleOnline gem uses its own connection mechanism and the logging hook will be available
only in versions more recent than 8.15.

Testing Done: tested the integration with the Kill Bill Litle plugin (see http://kill-bill.org).

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
paypal: fix dereference error in paypal_express_response

Calling PaypalExpressResponse#address when the response didn't contain
any address information was causing a dereference error:

  NoMethodError: undefined method `[]' for nil:NilClass

Testing done: verified the dereference error doesn't happen
by issuing a SetExpressCheckout API Operation with an invalid
security header.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
Adds support to Paypal CreateBillingAgreement
litle: support paypage registrations

Allow to pass a paypageRegistrationId in the store() call, instead of a
credit card.

Testing Done: tested the integration with the Kill Bill Litle plugin
(see http://kill-bill.org).

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
Merge branch 'paypal-express-fixes' into fixes-for-kill-bill
Merge branch 'add-logging-support-for-litle' into fixes-for-kill-bill
Merge branch 'add-paypage-support-for-litle' into fixes-for-kill-bill