better help using abs, round etc, from numpy

[ofloveandhate]

for real_mp and complex_mp types

i want to be able to type

np.round(complex_mp)

or

np.abs(complex_mp)
```

and it just works

[ofloveandhate]

Addressed in #305 via helpers — bertini.abs / round / sum / norm / real / imag / conj / is_real over scalar / list / numpy array, staying mp-native (round uses Decimal so it keeps arbitrary precision). Note: overlaps with the native ufunc work on feature/numpy_compat — reconcile before closing.