Update beanstream_core.rb
Litle: Support optional fields with tokens

* Updated existing token based tests to pass optional fields in the
  options hash.
* Added missing certification tests for explicit token registration.
* Updated existing certification tests to use the latest documented
  data.
* Added support for processing a credit transaction with a token as well
  as a previous transaction id (identification).
* Updated certification specs based on direct feedback from Litle (some
  required data was missing).

Closes #575.
Add Finansbank gateway

https://www.fbwebpos.com/

Closes #591.
Paymill: Change `save_card_url` to use `.com`

This prevents the following error, when trying to do a purchase:

    OpenSSL::SSL::SSLError: hostname was not match with the server certificate

Closes #603.
WorldPay integration: Update endpoint urls

Closes #606.
Add Finansbank to README
Merge pull request #608 from anton-yordanov/d037370a071d089eddca599bdb470d4bc0b04d47

Beanstream: Add support for tax2
Add PayFast to README

Closes #612.
Braintree Blue: Set CC token in transaction hash

Closes #613.
Robokassa: Fix signature for empty amount

Closes #616.
Worldpay gateway: Fix error messages for failures

In particular, their docs state:

"A payment can only be cancelled after it has reached the status
AUTHORISED and can no longer be cancelled after it has reached the
status of CAPTURED."

and:

"Refunds can be processed after a payment has reached the CAPTURED
status. If a payment still has the AUTHORISED status, it can be
cancelled but not refunded."

Previously, if a transaction was in the wrong state, the error message
we were giving back was "SUCCESS", which was confusing to everyone.  Now
we explain why the operation failed.

We also now have some unit tests for the void operation.

Closes #614.
Worldpay gateway: Allow refunding settled payments

Closes #617.
Spreedly: Update urls and terminology

Closes #618.
Make card brand error more user friendly

Closes #619.
Authorize.Net CIM: Refund amount is optional

Closes #620.
DataCash: Fix typos in comments

Closes #621.
DataCash: Update test Mastercard number

Closes #622.
DataCash: Update test response fixtures

Closes #623.
Pin: Add Pin.js card token support

Adds support for passing in a card token to purchase and store with the
Pin gateway.

Closes #625.
Paypal Express gateway: Fix missing address

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

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

Closes #628.