Gateway and component bugfixes

• New error ComponentNotRunningError that will be raised when trying to interact with a component that is not running
• Actually closing when one of the shards has been manually shut down
• sent_close not being set when calling send_close
• Unused ratelimiter now hooked up to prevent getting disconnected on too many requests
• bot.shards is now populated as soon as the shard object is created to be able to be used through bot.x on shard events