v1.3.1: I don't like timezones

Don't be fooled by the bump in the minor version, this is significant functionality added to the bot: /jetze reports will now automatically also display historical data from the last month, further improving the ability of users to predict when mensa queues will be short. At least in theory, this data is messy.

• Graphic /jetze reports now include historical data from the last months, and will always display data from the last 60, as well as the coming 30 minutes
  • I just want to highlight that this feature is daylight saving time compatible
• Fix a breaking bug where the server would never shut down started chrome instances, and therefore become nonresponsive
• Fix a bug where times in graphs would be displayed in UTC instead of the actual mensa time
• MensaQueueBot is officially open source now, instead of unofficially
• We've also changed some non-repo backend things, and started the process of adding tests. As in, there's a single manual test now. Babysteps!