Add daily scheduled scale-in to 0 items for Auto Scaling Group

[obscurerichard]

To save money while we are testing this, we should spin down the auto scaling group to zero instances on a daily basis. That will set things up so that the only costs for running this without destroying it will be the elastic load balancer, which is only $19 per month, instead of hundreds of dollars per month.

We'd need to change the minimum size for the ASG in Terraform to 0, and also add the scheduled scaling event, probably for 02:00 UTC.