Allow any type of state variable

[matsulib]

I could use type numpy.ndarray or pandas.DataFrame for state variable from #12.
Unfortunately, the patch of #12 was canceled by ed97524.
There seems to be a little confusion.

I have a suggestion about this code.

class Annealer(object):
    def __init__(self, initial_state=None, load_state=None):
        if initial_state:
            self.state = self.copy_state(initial_state)
        elif load_state:
            with open(load_state, 'rb') as fh:
                self.state = pickle.load(fh)
        else:
            raise ValueError('No valid values supplied for neither \
            initial_state nor load_state')

To start annealing, I think only two things are required in __init__().
First, either initial_state or load_state is given.
Second, the given object is copyable. The definition of "copyable" can be custmized by overriding copy_state().

Therefore, all we have to do in __init__() is to check whether initial_state is given or not.
Other conditions about state can be handled by move() and energey(), so it doesn't matter if initial_state itself is evaluated as false like an empty list.

[perrygeo]

fixed by #20