Remove message history limit, add message count report

* When fetching the chat history, we don't use the default limit of 100
  and set it to unlimited.
* For every 1000 messages recorded in the history, we report that in the
  debug log.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

discord_markov/client.py

@@ -123,7 +123,7 @@ class Client(discord.Client):
         )
         count = 0
         skipped = 0
-        async for message in channel.history(after=last_message):
+        async for message in channel.history(after=last_message, limit=None):
             if message.author.bot:
                 continue
             if message.content.strip().startswith("!"):
@@ -131,6 +131,15 @@ class Client(discord.Client):
                 continue
             count += 1
             self.chain.add(guild.id, message.author.id, message.content, commit=False)
+            if count % 1000 == 0:
+                log.debug(
+                    "%s (%s) %s (%s) - %s messages",
+                    guild.id,
+                    guild.name,
+                    channel.id,
+                    channel.name,
+                    count,
+                )
         self.db.commit()
         log.info(
             "Guild %s (%s): channel %s (%s): synchronized %s messages (skipped %s messages that looked like commands)",