Support numpy structured arrays

[shaunc]

Currently paths for differences in numpy structured arrays are not readable:

>>> aa = np.zeros(1, dtype=(('a', (np.float32, (2,)))))
>>> bb = np.ones(1, dtype=(('a', (np.float32, (2,)))))
>>> '\n'.join(recursive_diff(aa, bb))
"[data][0]: b'' != b'1'"

[crusaderky]

Thanks for the suggestion @shaunc. While I don't plan to dedicate time to this feature myself, contributions are welcome!