script fails on policy simulations using KMS Id

[Mark Keisler]

policy simluations involving the KMS key supply its Id as an arg to --resource-arns and this throws an error:

An error occurred (InvalidInput) when calling the SimulatePrincipalPolicy operation: ResourceNames are not in a valid ARN format: 14a050d4-021e-4efe-84bb-0871bf6d0fda.

The arn should be looked up and used instead. #34 fixes this