Nits

[Hunternif]

• create target Topic make its id a string.

• remove field server_id.

• move types.py into markov.

• since I'm not using "silent mentions by name" anymore, remove this part:

  cheems-bot/cheems/discord_helper.py

  Lines 129 to 132 in b48d7ca

  	if hasattr(target, 'name'):
  	target_name = target.name.lower()
  	if text.lower().startswith(target_name):
  	text = text[len(target_name):].strip()

• fix test: compare with test data

  cheems-bot/tests/reaction/test_reactions.py

  Line 40 in 51c5ce0

  self.assertEqual(Server(), m)

• add serialization test for reaction model

• update comment

  cheems-bot/cheems/markov/markov.py

  Line 29 in f4449e2

  Adds new word sequences to data from the given sentence.

• use makedirs

  cheems-bot/cheems/markov/models.py

  Line 66 in bd75e68

  os.mkdir(subdir)