Docs Update - default value for with_public_ip and export outputs from metaflow module

[josephsirak]

Update docs:

1. Set the with_public_ip value in the README to true since the code already sets the public subnets
2. Export outputs from metaflow module to the top level project in the minimal setup example. Output:

+ metaflow = {
      + METAFLOW_BATCH_JOB_QUEUE                    = (known after apply)
      + METAFLOW_DATASTORE_SYSROOT_S3               = (known after apply)
      + METAFLOW_DATATOOLS_S3ROOT                   = (known after apply)
      + METAFLOW_ECS_S3_ACCESS_IAM_ROLE             = (known after apply)
      + METAFLOW_EVENTS_SFN_ACCESS_IAM_ROLE         = (known after apply)
      + METAFLOW_SERVICE_INTERNAL_URL               = (known after apply)
      + METAFLOW_SERVICE_URL                        = (known after apply)
      + METAFLOW_SFN_DYNAMO_DB_TABLE                = (known after apply)
      + METAFLOW_SFN_IAM_ROLE                       = (known after apply)
      + api_gateway_rest_api_id_key_id              = (known after apply)
      + batch_compute_environment_security_group_id = (known after apply)
      + datastore_s3_bucket_kms_key_arn             = (known after apply)
      + metadata_svc_ecs_task_role_arn              = (known after apply)
      + metaflow_api_gateway_rest_api_id            = (known after apply)
      + metaflow_batch_container_image              = ""
      + metaflow_profile_json                       = (known after apply)
      + metaflow_s3_bucket_arn                      = (known after apply)
      + metaflow_s3_bucket_name                     = (known after apply)
      + migration_function_arn                      = (known after apply)
      + ui_alb_arn                                  = (known after apply)
      + ui_alb_dns_name                             = (known after apply)
    }