Fix failing remote test.
Initial commit of eWay Rapid 3.1 changes.

I've rewritten this to use the new JSON API.  I also removed the sandbox
credentials from the shared fixtures.yml since this was tied to a
specific eWay sandbox account and these credentials do not support the
new 3.1 direct transactions.
Finish eway rapid 3.1 gateway.

Finish refund implementation.  Add unit tests. Update rdocs.
Mark the eway direct credentials as invalid.
Merge pull request #1176 from Shopify/eway_rapid_3.1

Eway rapid 3.1
Add Cashnet gateway

http://www.higherone.com/

Closes #1166.
Conekta: Standardize address options

Closes #1154.
Wirecard: Add support for reference purchases

Closes #1192.
Eway Rapid: Update country list

I don't see anywhere on the eWAY website to suggest that Rapid has any
availability difference from the straight up eWAY gateway.  Added New
Zealand and the UK to the list.

Closes #1194.
Send along proper version header for Balanced gateway.

Closes #1196.
Handle 1.0 errors and 1.1 errors
update 404 leetsoft.com links
update Gestpay url
Worldpay: Add support for external references

This allows referencing a transaction made in a different merchant
account by passing the :merchant_code option.

Also updates the DTD being used for Worldpay.

Closes #1081.
Fix unit tests hitting real API's
Sort fixtures file

And add a test that ensures it stays that way.
Merge pull request #1199 from alepore/gestpay_url

Update Gestpay URL in README.
Merge pull request #1198 from alepore/user_agent_url

Fix old leetsoft.com references
Balanced: Voiding a capture is not allowed

Balanced only allows authorizations to be voided.  Previously, if
someone attempted to void a capture, it would raise a TypeError since it
as trying to append a string to nil.

Now we return a failed Response.

Closes #1201.
Add HPS gateway (Heartland Payment Systems)

http://developer.heartlandpaymentsystems.com/SecureSubmit/

Closes #1069.