NetworkUnit not compatible with Neo 0.10

[heplesser]

NetworkUnit requires NeoHdf5IO

https://github.com/INM-6/NetworkUnit/blob/d882c55ea9321523553a3fafcb79d2df19536906/networkunit/models/model_spiketrain_data.py#L5

which has been removed with Neo 0.10.0 (NeuralEnsemble/python-neo#951).