Optimize sliding window kurtosis

[amaggi]

Set up a 2D array where each row is a window, and send to ss.kurtosos . To set up sliding window, try following code:

def window(seq, n=2):
    "Returns a sliding window (of width n) over data from the iterable"
    "   s -> (s0,s1,...s[n-1]), (s1,s2,...,sn), ...                   "
    it = iter(seq)
    result = tuple(islice(it, n))
    if len(result) == n:
        yield result    
    for elem in it:
        result = result[1:] + (elem,)
        yield result

[amaggi]

Implemented in dev. Now test that sw_kurtosis1 and sw_kurtosis2 in filters give the same result.