A standard Dynamic Time Warp match of two sequences of feature
vectors. The allowed time increments are (0,1), (1,0), and (1,1).
 Parameters:
x (numpy.ndarray, 2dimensional. First index is the time axis,
second index is the feature axis.)  one array of feature vectors
y (numpy.ndarray, 2dimensional. First index is the time axis,
second index is the feature axis.)  the other array of feature vectors
alpha (float)  exponent for differences in features. 2=Euclidean, 1=city block
beta (float)  exponent for summing along time axis. Normally 1.
 Returns: numpy.ndarray, 2dimensional array of integers with shape [n,2].
[i,0] is the index (time) in x, [i,1] is the index (time) in y.
 An array that maps from indices in x to indices into y. x[r[i,0]]
matches y[r[i,1]] for all i.
