support numpy types by escaping type numbers.Real

[devinstevenson]

numpy int64 and float64 inconsistently derive from base int and float depending on python version. Checking against numbers.Real ensures correct behavior.

on python 3.6

>>> import numpy as np
>>> import numbers
>>> 
>>> isinstance(np.int64(1), int)
False
>>> isinstance(np.float64(1.), float)
True
>>> isinstance(np.int64(1), numbers.Real)
True
>>> isinstance(np.float64(1), numbers.Real)
True

on python 2.7

>>> import numpy as np
>>> import numbers
>>> 
>>> isinstance(np.int64(1), int)
True
>>> isinstance(np.int32(1), int)
False
>>> isinstance(np.float64(1.), float)
True
>>> isinstance(np.float32(1.), float)
False
>>> isinstance(np.int64(1), numbers.Real)
True
>>> isinstance(np.int32(1), numbers.Real)
True
>>> isinstance(np.float64(1), numbers.Real)
True
>>> isinstance(np.float32(1), numbers.Real)
True

@jingw Please review. Thanks.

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