Attributes table in documentation formatting problem

**Original issue:** https://github.com/rlabbe/filterpy/issues/142
**Created:** 2018-06-24
**Last updated:** 2018-06-24

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It uses the standard NumPy formatting convention of
    x : numpy.array(dim_x, 1)
        State estimate vector

but displays with type intermixed with description:

x | (numpy.array(dim_x, 1)) state estimate vector