Implement building with docker

See the README for usages and details.

A breaking changes here too:
* run.py is gone, we now handle that kind of thing with docker
* The token is out of the config and is now an ENVAR (ideally using a .env)
* `.json` files are now in a .matchy/ subdirectory, as this makes it a lot easier for the container to safely read

Bonus:
* fix a score_factors.setdefault call causing issues
* Reformat some of the readme

py/matchy.py

@@ -4,12 +4,12 @@
 import logging
 import discord
 from discord.ext import commands
-import config
+import os
 from state import load_from_file
 from cogs.matchy_cog import MatchyCog
 from cogs.owner_cog import OwnerCog
 
-_STATE_FILE = "state.json"
+_STATE_FILE = ".matchy/state.json"
 state = load_from_file(_STATE_FILE)
 
 logger = logging.getLogger("matchy")
@@ -35,4 +35,6 @@ async def on_ready():
 
 if __name__ == "__main__":
     handler = logging.StreamHandler()
-    bot.run(config.Config.token, log_handler=handler, root_logger=True)
+    token = os.environ.get("TOKEN", None)
+    assert token, "$TOKEN required"
+    bot.run(token, log_handler=handler, root_logger=True)