Pull Request that contemplates Issue #13

These codes doesn't alter methods signature and not messing the existing behavior in the library.
I just check if the user check "Only published contents" and them I verify if the node has publication:currentState with published value.
Boubaker,

I do on this way to not change exportSite method signature. If you see a some parameters are passing to this method and I need to include more one, to avoid change method signature I needed to create a instance variable.