adds signature to card_stream_modern.rb and ports over some features of card_stream.rb
CRITICAL FIX: AVS fails for people with a flat number,
Remove CardStream legacy and replace it with CardStream Modern gateway
Fix CI

Exclude rails 23 + ruby 2.1.0 on tests
Only display travis status from master.
Merge pull request #1021 from Shopify/cardstream_signature

Cardstream P3 upgrade
Update CHANGELOG for 1.42.5 bump
Bump AM version to 1.42.5
Adjust conekta integration to use :login
Update few asserts in Conekta remote tests
Update fixtures and fix one more test
Merge pull request #1031 from Shopify/fix_conekta

Change Conekta gateway to use :login instead of :key
Litle: Truncate order_id

Litle requires the order_id to be a maximum of 25 characters.

Closes #1034.
Conekta: Fix #refund; respect :currency

Refund parameters were backwards causing "money amount must be a
positive Integer in cents.".

Currency parameter was not being respected.

Closes #1015.
SagePay: Truncate description field

If a description longer than 100 characters is specified, SagePay fails
the transaction with this error message:

3082 : The Description value is too long.

Now we truncate the description to match SagePay's constraint.  This
simplifies the code of those using Active Merchant since they won't need
to conditionally account for SagePay's description contraint.

Closes #1017.
PlugNPay: Fix some remote tests

The PlugNPay test gateway now requires the name to have 'cardtest' for
the transaction to work.  This change gets some of the remote tests to
work again.

I'm still having difficulty with the remote tests for capture, void, and
refund.  Tech support for PlugNPay says that those operations are not
supported on their test gateway.  And they confirmed this fact on the
phone.

I'm hesitant to remove the remote tests for capture, void, and refund
though since they've been added in the past and they were clearly
working for someone at some point.  I don't know if PlugNPay adjusted
their test gateway to no longer support them.  Or if their tech
support is simply wrong and that there's actually some gateway setting
needed to enable those operations.  I'll leave those tests for now.

Closes #1020.
Paymill: Add 3 more supported countries

Closes #979.
Use new badge with rating for Code Climate

Closes #1007.
Fix yard doc ignoring README

Closes #1010.
Added Cecabank gateway (Spain)

http://www.ceca.es/es/

Closes #1006.