Document how to set up authentication

[Nilzor]

Out of the box dsnap list says botocore.exceptions.NoCredentialsError: Unable to locate credentials. I can't seem to find anything in the README about how to set up credentials

edit: I see the "IAM Permissions" section but I don't know how that relates to the credentials file and how that relates to the IAM settings at AWS

[RyanJarv]

So dsnap uses the default AWS credential lookup behavior, so you should be able to use credentials in the same way as the aws cli. Which would be in the environment, then the default profile, unless you explicitly use a different profile with --profile or AWS_PROFILE

Granted, I believe there may be an issue with setting the profile in the environment currently. If so you can use the --profile flag explicitly.

I agree this would be a good thing to document however.