[NixIO] Cleanup set up conditionals
[NixIO] Cleanup set up conditionals

Tests classes are skipped conditionally instead

theunissenlab/python-neo,rgerkin/python-neo,apdavison/python-neo,samuelgarcia/python-neo,JuliaSprenger/python-neo,INM-6/python-neo,NeuralEnsemble/python-neo