merging.py: flake8, shortened inputs w/ __init__
anaphoricity.py: flake8, renamed vars
util.py: flake8, added import errno
rst.py: flake8, string formatting
mmax2.py: flake8, outsourced has_antecedent(markable)
exmaralda.py: flake8, outourced is_informative(layer)
flake8 shall ignore __init__.py b/c of unused imports
- all of these imports would have to be added to __all__ to
  get around this
flake8: discoursegraph.py, conano.py