If beanstream finds a stored customer profile which is a match, use it and continue.

Fixes #87
Add ActiveMerchant-backed USAEpay gateway

Caveat:  Shopify/active_merchant#757 is outstanding. If you try to use this gateway in 'test' mode, it will not work until that PR has been merged.
Added pay_to_email in the config and to the skrill request

Fixes #88
Add Pin gateway

Conflicts:
	lib/spree_gateway/engine.rb
Remove old files.
Fix UsaEpay spec so it pass.

- Replace old syntax.
- Make it readable ;)
- purchase! in lambda
- Add provider_class test to reach 100% coverage