ActiveMerchant 1.21.0 released

[John Duff]

There's lots of changes in this release, thanks to ntalbott for
reviewing and merging most of these in and everyone who contributed.

We have three new gateways in this release: CertoDirect, NAB Transact
and Authorize.net SIM. Most of the remaining changes are bug fixes,
with a few additional features on existing gateways.

The full details from the change log are below:

* Stripe: Add support for passing IP [collision]
* Merchant e-Solutions: pass expiration date when purchasing with a
stored credit card [chrisyoung]
* Braintree: Fix passing custom processor ids to old accounts
[maxsilver]
* Authorize.net CIM: Add validation mode option to
create_customer_profile_request [jwood]
* eWay Managed: Include transaction number in response params [jamsi]
* Fix various hash ordering issues exposed by Ruby 1.8 [ntalbott]
* Authorize.Net CIM: Add WEB echeck type [deathbob]
* Move Braintree from the gemspec to the Gemfile [ntalbott]
* Add CertoDirect gateway [hron]
* Authorize.Net CIM: Add option for setting a custom delimiter
[bmorton]
* Authorize.Net CIM: Add 3.1 response fields [bmorton]
* Authorize.Net CIM: Misc fixes and doc improvements [bmorton]
* Authorize.Net CIM: Fix error when order is blank [KeeperPat]
* Beanstream: Add recurring payments support [castiglione]
* Make ePay password optional [ePay]
* Quickpay: skip testmode if transaction provided [brentmc79]
* Payflow: add additional fields [thorstadt]
* Authorize.Net CIM: Add get_customer_profile_ids [howaboutwe]
* PayPal Express: Add support for BrandName and Custom fields [exviva]
* Payflow: Handle dates with leading zeros [jcoleman]
* Authorize.Net CIM: Add CCV code support & improve tests [tgarnett]
* Add Authorize.Net SIM integration [courtland & rdp]
* Secure Pay AU: Handle periodic payments [tommeier]
* Viaklix: Add discover as a supported card type [waelchatila]
* Improvements to testing infrastructure for integrations [jduff]
* Add NAB Transact (AU) Gateway [tommeier]