Performs an entropy analysis based on zlib compression ratio.
        This is faster than the shannon entropy analysis, but not as accurate.

def gzip(self, data, truncate=True):
        '''
        Performs an entropy analysis based on zlib compression ratio.
        This is faster than the shannon entropy analysis, but not as accurate.
        '''
        # Entropy is a simple ratio of: <zlib compressed size> / <original
        # size>
        e = float(float(len(zlib.compress(str2bytes(data), 9))) / float(len(data)))

        if truncate and e > 1.0:
            e = 1.0

        return e