Use u-strings instead of 'import unicode_literals'
Use u-strings instead of 'import unicode_literals'

isinstance(u'', str) returns False in Python 2,
so importing unicode_literals causes several tests to fail

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