Rewrite toArray and toString to work for multidimensional arrays

[mateogianolio]

Currently toString only prints the data in one dimension.

See examples below for a good representation.

One dimension

>>> np.arange(12)
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11])

Two dimensions

>>> np.arange(12).reshape(6, 2)
array([[ 0,  1],
       [ 2,  3],
       [ 4,  5],
       [ 6,  7],
       [ 8,  9],
       [10, 11]])

Three dimensions

>>> np.arange(12).reshape(3, 2, 2)
array([[[ 0,  1],
        [ 2,  3]],

       [[ 4,  5],
        [ 6,  7]],

       [[ 8,  9],
        [10, 11]]])