Allow specifying session token

[flying-sheep]

This is useful for local testing using something like gimme-aws-creds

[auvipy]

should this change also need mentions in docs?

[flying-sheep]

Oh, probably!

We might also want to think about how to mention it, because it’s not something for production code – a session token is only valid for a while, so this is for testing your code locally, while you’d be using roles on AWS.

But it is useful. I’d have had a hard time verifying that my project works without this.

[matusvalo]

@flying-sheep I think at least you can comment the method itself and also you can put a note to docstring of the module.

[flying-sheep]

done!