Remove Sandbox URL config option.
Always use Gateway URL config value.

fixes issue 6

Fixes issue 3

Fixes issue 4

Fixes issue 7

Addresses feedback in issue #6

Addresses feedback on issue #16

Changed the hidden form from being generated on the server side to
be generated on the client side instead. Added event listeners to
update the form as user details are modified.

Added scope settings to allow branding configuration to be changed
at the store level. Updated front end code to request data in the
correct scope.

Changes should fix issues #10, #17, #18 and #22.

Added the "Payment from Specific Countries" field to the config,
restricted to only allow selction of AU and/or NZ. This is a
built in Magento field that hides the payment option if a country
outside of the selected values is set for shipping.
Added error checking to stop orders from outside the selected
countries. This is primarily for billing address, but also checks
the shipping country in the cases where the magento logic fails.
Improved error checking functionality and error display in the
checkout.

Fixes issue #8

Addresses feedback on issue #16

Addresses feedback on issue #8