weep export to use the profile name instead of ARN

[igr]

Look at the following example:

aws --profile foo sts get-caller-identity
eval $(weep export arn:aws:iam::123:role/PowerUser)

It would be great if we could use the profile name for weep instead of the ARN. This information is stored in ~/.aws/config, it is easy to parse (configparser style).

The usage could look like:

weep export foo

or, better

weep export --profile foo