pd.Series are converted to np.ndarray #40
Description
When a pandas series is passed to iniabu as the vector for isotope ratios, it will turn it into a numpy array and return it. However, if a Series is passed, it would be great if a Series would be returned and no change takes place. Might also need some documentation changes.
Labeling this an enhancement instead of a bug since the docs at the moment state that an np.ndarray will be returned.