Updates moving average code to remove use of numpy.

This is needed because numpy arrays cause issues with serialization.

@oxtopus please review
@breznak fyi - let me know if you see any issues
@scottpurdy: Since `self.slidingWindow = []`, wouldn't `self.total = float(sum(self.slidingWindow))` be just `0.0`? Why use the more complex expression to initialize it?