Implement PlexPartialObject json serialization

[tdorsey]

Use marshmallow to do it? refs pushingkarmaorg/python-plexapi#190

[IMCAgro]

HI
I had make serialize with jsonpickle
Its work perfect
There are two problems

1. Its serialize everything - so need use handlers

class PlexJsonHandler(jsonpickle.handlers.BaseHandler):
   def restore(self, obj):
       pass

   def flatten(self, obj, data):
      # Fix url raise
       if isinstance(obj, PlexClient):
         setattr(obj, "_baseurl", PLEX_URL)
       #remove methods, private fields etc
       members = [attr for attr in dir(obj) if not callable(getattr(obj, attr)) and not attr.startswith("__") and not attr.startswith("_")]
       for normal_field in members:
           # we use context flatten - so its called handlers for given class
           data[normal_field] = self.context.flatten(getattr(obj, normal_field), {})
       return data

And register handler
i am using for parent class , so all gone be called
jsonpickle.handlers.registry.register(PlexObject, PlexJsonHandler, True)

Use
unpicklable - mean - just decode without back encode to the python class
str = jsonpickle.encode(session, unpicklable=False)

Here is session

Need make PR?