Port existing parsers over to new parser/generator interface

[wstrinz]

I've recently added a more standardized interface for the process of transforming input data to RDF, which existing Publisci::Readers classes should eventually be converted to.

Having a controlled interface will allow me to continue adding features such as new serialization formats without breaking existing transformers, and will help other understand and improve transformer code more effectively.

Currently this new format is not documented anywhere, but if someone is interested in tackling this issue I can make sure to write some!