classes with extra dependencies should fail on init rather than import so the docs still build
update test skips
update which versions of python 3 are compatible
all io modules should always import
fix potential bug in alphaomegaio and plexonio with multi-datatype format strings
remove line that could never be reached in analogsignal
cleanup imports
fix testing issue with hdf5io nested function scope
minor pyflakes cleanups
fix missing and unneccessary variables in neuroshareio
fix bug in error message string in test.tools
fix getattr and setattr in spike2io HeaderReader
fix missing and unneeded variables in plexonio
fix bug where elphyio could return a list then call to_list on it