v0.6.0 Clone with Snapshot Restore

• Added the ability to clone with source and target instances in different VPCs, by automatically falling back to RestoreDBInstanceFromDBSnapshot, instead of CreateDBInstanceReadReplica.
  The restore will be done based on the latest snapshot available, which is usually at most 24h stale.
• Added --restore-snapshot to force even same-VPC clones to be done with RestoreDBInstanceFromDBSnapshot (it's currently faster)
• Added a terraform environment for testing

v0.5.0 IAM Policy Generation

• Added --iam-policy option for generating a IAM policy for a user or role to clone a replica with a minimal set of permissions.
• Updated dependencies