[Mollie] Use description option in helper to set the order's description when generating the redirect URL
Merge pull request #1146 from Shopify/mollie_order_description

[Mollie iDEAL] Use description option in helper to set the order's description
Leave one blank line below 'private'

More readable and eye appealing ;)

According to: ruby-style-guide ( https://github.com/bbatsov/ruby-style-guide/blob/master/README.md#classes--modules )

` Leave one blank line above the visibility modifier and one blank line below in order to emphasize that it applies to all methods below it.`
Validate Gateway.supported_countries

Validate that the list of supported country codes sent to
Gateway#supported_countries contains only valid entries (according
to active_utils' ActiveMerchant::Country definition).

This necessitated the modification of some existing gateways'
supported_countries lists. In most cases a mapping to the correct
country code was made. However, in rare cases the invalid country
code was removed and no meaningful new value was substituted.

Closes #1142.
Adds support for Klarna and cart line items
Fixes Klarna-related tax rate calculation test + behaviour
Merge pull request #1147 from Bartuz/patch-1

Leave one blank line below 'private'
Fix Travis CI
Merge pull request #1150 from Shopify/fix_travisci

Fix Travis CI
Add support for recurring flag on Stripe
CHANGELOG
Check value of eci
Review feedback
Add :recurring option
Fixes for Klarna
* Cart items unit prices always include taxes by adding the passed in unit price + passed in tax amount
* Currency from Notification is always upcased
* Append order id as query param to merchant_push_uri and merchant_confirmation_uri
* Return status 'Completed' and not 'Complete'
Merge pull request #1152 from Shopify/stripe_recurring

Add support for recurring flag on Stripe
Use localized amounts for Stripe
Update WebPay
CHANGELOG
Fix param passing