IntervalIndex nbytes computation

[TomAugspurger]

Currently, it looks like IntervalIndex.nbytes just uses IndexOpsMixin.nbytes

@property
def nbytes(self):
    """ return the number of bytes in the underlying data """
    return self._values.nbytes

Should it instead be self.left.nbytes + self.right.nbytes? This will be faster, and I think more correct.

[jschendel]

Should it instead be self.left.nbytes + self.right.nbytes?

That makes more sense to me. Not sure exactly what the use case of nbytes is though, so really just basing this off the docstring description.