Use Manager::parseIncludes with TrasformerAbstract

Creating a small change for TransformerAbstract for use parseIncludes into it.
(PR for issue #67 )
You're right for both segnalations. 
I think this setCurrentIncludes method could to be set as protected, because i use that in processIncludedResources of TransformerAbstract method.

With this edit, it seems i'll be able to use "include" GET parameters for included data from URL.

EXAMPLE ENDPOINT: 

http://api.sample.com/campaigns?include=client


I use this edit in a project actually and it seems works properly. 
Can you give me a better solutions? :)

Thanks a lot!