add remote track tests
abstract payment tokens
add unit tests for apple pay xml injection
add placeholder remote tests for auth.net apple pay transactions, fix whitespace
Add error_code to ActiveMerchant::Billing::Response and use it with strip error codes
added mercury certification test cases
Revert "added mercury certification test cases"

oops
This reverts commit d3475044a8b2f59f4bed279a8cfb42da11f7ba12.
added credit_card_track_data method
Merge pull request #1435 from Shopify/error_codes

Standardizing error codes
Conekta: Add a remote test

There is some functionality in the Conekta gateway allowing one to
specify things like line items and customer name using the options hash.
We now have a remote test actually hitting it.
TNS: Update countries and supported card types

Closes #1440.
Conekta: Add AMEX as a supported card type

Closes #1424.
auth_net should take care of encoding apple pay token as needed
replace Authorize.Net credentials with Apple Pay-enabled ones
move apple_pay_payment_token into Auth.Net remote tests, since all data is specific to Auth.Net, simplify apple pay token tests
review items: mention freshness of test credentials, realistic instantiation of ApplePayToken objects in test, style polish
Merge pull request #1437 from Shopify/authorize_net_apple_pay

Payment Tokens, Apple Pay Payment Tokens, Authorize.Net Apple Pay support
changed method name
Merge pull request #1431 from Shopify/firstdata_track_remote_tests

add remote track tests to firstdata_e4
fixed error