Slack bots no longer auto-join #general. [ci skip]
Slack bots no longer auto-join #general. [ci skip]

slack-ruby/slack-ruby-bot-server,johnhenriksson/dailybitsof-slackbot,dblock/slack-bot-server,dblock/slack-amber-alert,dblock/slack-bot-server,dblock/slack-amber-alert,johnhenriksson/dailybitsof-slackbot,johnhenriksson/driftbot,dblock/slack-bot-server,dblock/slack-ruby-bot-server,dblock/slack-amber-alert,dblock/slack-ruby-bot-server,slack-ruby/slack-ruby-bot-server,johnhenriksson/dailybitsof-slackbot,johnhenriksson/dailybitsof-slackbot,johnhenriksson/driftbot,slack-ruby/slack-ruby-bot-server,dblock/slack-bot-server,johnhenriksson/driftbot,dblock/slack-ruby-bot-server,johnhenriksson/driftbot