ProcessManager.bind_state_fields doesn't work with multiple states

[khamenman]

Currently there is a bug with ProcessManager.bind_state_fields method as it utilizes closures incorrectly:

for state_field, process_class in kwargs.items():
    if not issubclass(process_class, Process):
        raise TypeError('Must be a sub class of Process')
    parameters[process_class.get_process_name()] = property(lambda self: process_class(
        field_name=state_field,
        instance=self))
    parameters['state_fields'].append(state_field)

With this code, value of the process_class variable inside the lambda function will always be the last class passed in kwargs to bind_state_fields method.