Several Bugfixes

### Bugfixes

* Fixes Issue https://github.com/infopark/crm_connector/issues/1 : Inheritance of Schema.
* With Active Resource 3.0 it accidentally uses XML instead of JSON. This Pull-Request fixes this.
* Fixed/Refactored some broken tests.

### Cruise

Green Crm Connector Cruise: http://cruise.infopark:3000/project/show_build/15019