ActiveMerchant 1.20.0 released

[John Duff]

*Note: This release still supports Rails 2. We also skipped 1.19.0 due
to a hiccup in the release process.

We've had a number of pull requests merged with fixes and added
features to various gateways. We also have a new gateway added,
Samurai by Fee Fighters (https://samurai.feefighters.com/), supporting
US merchants at the moment.

Full change log for this release:

* Add support for USA ePay Advanced SOAP interface [matthewcalebsmith/
jduff]
* Beanstream: fix purchase with Secure Profile [pitr/jduff]
* Orbital: various fixes [Soleone]
* Add Samuari gateway by Fee Fighters [jkrall/odorcicd]
* Lock money gem to 3.7.1 or less since newer versions break in 1.9
[jduff]
* Braintree: handle gateway rejected transactions gracefully
[braintreeps/jduff]
* Ogone: support different signature encryptors, custom currency and
eci [ZenCocoon/rymai/jduff]
* Payflow Link: use secure token [jduff]
* Added refund method to Exact, Pay Junction and Skip Jack gateways
[jduff]
* Elavon: added test url [kylekeesling/jduff]
* Fix redundant errors when credit card is expired [castiglione/jduff]
* Two Checkout: update service url [vampirechicken/jduff]