Pypayex

Added Travis deployment.

* 6, 7: Updated URLs to the test environment

Fixes and additions from https://github.com/edqu-ab.

* Replaces Initialize7 with Initialize8 handler.
* Adds AddSingleOrderLine2 and PurchaseInvoiceCorporate handlers.
* Adds pypayex specific alternative names of proxy variables.

Thanks to [alexbrasetvik](https://github.com/alexbrasetvik) for these patches.

* Added PxCredit5 and PxCheck2 handlers.
* Properly deal with dicts and lists when normalizing.

[..]