Persist scoreboard

[turt2live]

If the bot restarts then it loses track of all of the scoreboard data. It should persist it somewhere in case it is restarted.

Specifically:

• What is currently on the scoreboard
• What the vote count is (though this can be retrieved from the server with /aggregations)

[squahtx]

Closing this.

As noted by Travis, the bot resumes syncing from where it left off, so the chance of missing a vote is minimal except for one
corner case, which has been filed as #92.