Cybersource gateway: Add support for subscriptions

Adds support for #store, #update, #unstore, and #retrieve. Also adds the
ability to use a subscription code with #authorize and #purchase.
eWAY gateway: Update docs. Require address.

Docs:

* Remove old copy & paste about TrustCommerce.
* Add info about transaction results.
* Add test credit card number, provided by eway docs
  (http://www.eway.com.au/developers/sandbox/direct-payments.html)

Code:

* :order_id is not a required parameter, so remove it
* Add :address and :billing_address to required parameters, because if
  you don't pass address to gateway, you'll get:

    Error: Required XML tag(s) missing, or incorrect case used. Required tag Name(s): ewayCustomerAddress, ewayCustomerPostcode

* Remove tests for invalid expiration date and verification value.
  Seems like the Test eWay Gateway doesn't care about the validity of
  them and always returns a success code.

Closes #378.
Braintree Blue gateway: Always pass CVV on update

Always passing the CVV allows for "updating a credit card and explicitly
verifying the card" at the same time:

https://www.braintreepayments.com/docs/ruby/general/card_verification#credit_card_api

Closes #380
Add Fat Zebra gateway

Closes #377
Braintree Blue gateway: Support wiredump_device

For example:

    ActiveMerchant::Billing::BraintreeBlueGateway.wiredump_device = Logger.new(STDOUT)

Also, a developer can now set the Braintree logger level
(+Braintree::Configuration.logger.level) without having it overwritten
by ActiveMerchant.

Previously, ActiveMerchant was forcing the Braintree logger level to be
Logger::ERROR when a BraintreeBlueGateway was instantiated, even if an
explicit log level was already configured.

There is no reason for ActiveMerchant to set the Braintree logger or the
log level (unless wiredump_device is set) since the Braintree gem sets a
sane default already.
Add the Metrics Global gateway

Copied the Authorize.net gateway and stripped out the functionality that
is not applicable.

Updated the tests to account for the slight differences in response
format.

Added the public demo account information to the fixtures.yml file.

Added the appropriate documentation for the gateway.

Closes #382
Cybersource gateway: Move email requirement

The email field is not required for subscriptions, so this moves it
under add_address so it only affects standard transactions.

Closes #383
Cybersource gateway: Fix updating address only

Allows one to update a CyberSource subscription billing address only
(without the need to pass a credit card again).

Closes #387
Clean up requires of RubyGems and JSON gems. Rename remote Litle test to match naming conventions.
ignore *.orig files
Wirecard gateway: Fix for missing address hash

If the address has was not passed in, the gateway would throw an error
when attempting to pull the country information out of the non-existent
hash.

Fixed via a general cleanup of handling the options hash; previously,
the @options instance variable was overwritten with call specific
options. Now the @options is merged with the passed in options, and
the instance variable isn't ever touched.

Also did general formatting cleanup, and refactored how the request is
built.
Adding paypal payments link
Authorize.Net gateway: Improve #refund docs

Added a note that makes it clear you can pass just the last four of the
credit card number in order to initiate a refund.

Closes #389
Whitespace errors are the best kind of errors. Fixed that for great justice.
Removed a bunch of unncessary classes and unneeded code
Merge pull request #392 from Shopify/paypal/payments_advanced

Add PayPal Payments Advance as a payment processor for Active Merchant
Fix payflow link
USAepay gateway: Add description support

This adds support for the description field to the USAepay Transaction
gateway.

Also fixes up the remote tests a bit, and cleans up some spurious white
space.

Closes #391
Updating LitleOnline requirement to 8.13.2 to take advantage of better validation and get bugfix for Username/Password
Merge pull request #394 from LitleCo/master

Litle & Co bump dependency