Remove cert binding

Remove cert binding (#2)

* Remove cert binding
* Update Curl Agent info
* Delete paymill.crt
* Update CHANGELOG.md
* Update config.xml
* Update pigmbhpaymill.php

Integration of PayFrame to enable use of SAQ A for easier PCI DSS 3.0 compliance

Merge pull request #1 from PrestaShop/master

Merge with PrestaShop/pigmbhpaymill