Support for serialization with jsonpickle

In my application i am serializing the state using jsonpickle. Therefor `state_pickler.State` needs two additional functions implemented to support this. Maybe you consider adding this to main.

```
    def __getstate__(self):
        return dict(self)

    def __setstate__(self, state):
        dict.__init__(self, **state)
        self.__dict__ = self
``` 