Swap out REXML for Nokogiri in payflow common parser.

REXML is very strict with its xml parsing so fails hard on invalid
characters, Nokogiri strips them and continues on. This is a much better
experience for ActiveMerchant users.

I've only replaced the parser in Payflow common, but we should work on
moving everything to Nokogiri since it is a much better XML parser.
Merge pull request #673 from jduff/use_nokogiri_parser_with_paypal

Swap out REXML for Nokogiri in payflow common parser.
Transliterate the description for Payflow Link
Remove non-ASCII characters using gsub when transliterate isn't available
Fix Payflow Link tests for 1.8
Merge pull request #674 from Shopify/payflow_link_transliterate

Transliterate the description for Payflow Link
Paymill: Change .com -> .de

This fixes an issue where card tokenization was failing in production.

Also uses the correct marketing form - PAYMILL - and adds some supported
countries.

Closes #672.
Quickpay integration: Fix v6 response parsing

The regexp didn't work with the actual input directly from Quickpay.

Closes #661.
First Data e4: Add store support via TransArmor

TransArmor is an API extension for implementing card number
tokenization.

Closes #563.
MerchantWarrior: Format expiration correctly

According to the MerchantWarrior API documentation, cardExpiryYear and
cardExpiryMonth must meet these conditions:

  cardExpiryMonth
  Example: 05
  Notes: This must be in MM format. The month must be zero-padded if
         it’s less than 10.
  Valid Length: 2 digits.

  cardExpiryYear
  Example: 13
  Notes: This must be in YY format.
  Valid Length: 2 digits.

Closes #665.
Add iconv for ActiveSupport 2.3 under Ruby 2.0
Require Ruby 2.0 compatibility in Travis-CI

Closes #669.
Fix duplicate test methods

A bunch of test methods were duplicated, meaning the first version of
them was not being run. This was revealed by running under Ruby 2.0,
since its test/unit warns about the duplication.
DataCash: Fix remote tests

Closes #670.
Fix GettingStarted.md reference links in README

Closes #671.
Add Transnational gateway

http://www.tnbci.com/

Closes #675.
Authorize.Net: Add Check as a payment method

Closes #676.
Merchant e-Solutions: Add ref# and recurring

Adds client_reference_number on each operation and enables recurring
operations.

Also catches 404's from MeS if URL is wrong because of MeS system issue.

Closes #648.
Bogus gateway: Add authorization to response

Most (if not all) gateways add 'authorization' to response of purchase
transaction. It allows developer to use returned 'authorization' as a
payment source for subsequent transactions in some
gateways (PayJunction for example).

To test this behavior properly it makes sense to have BogusGateway to
return 'authorization' in purchase response too.

Closes #677.
Bluepay: Add Check support; general cleanup

Brought the gateway into better alignment with AM coding standards.

Also fixed an issue with the wrong value being passed for checking
accounts. Unable to get a passing remote test due to not having a test
account set up for checks, but the new error looks more reasonable.

Closes #678.