Add _get_means() method in readout_analysis.py (SSRO)
Add _get_means() method in readout_analysis.py (SSRO)

- Add _get_means() method similar to the one in tda, and correct the call to the
plotting function such that the list of means is passed instead of the dictionary
of the mean of the data points.

QudevETH/PycQED_py3