Added an alt valid schema (role_arn & source_profile) to addProfile

[rmtuckerphx]

Both schema are valid as so should be able to add a profile using the alt schema:

[dev-admin]
role_arn = arn:aws:iam::555555555:role/admin
source_profile = master-user

[master-user]
aws_access_key_id = a
aws_secret_access_key = b

[coveralls]

Coverage remained the same at 100.0% when pulling f2e0724 on rmtuckerphx:master into 1799b86 on novking:master.

[novking]

https://docs.aws.amazon.com/cli/latest/topic/config-vars.html#using-aws-iam-roles
i believe credentials only have aws tokens. the "role_arn" and "source_profile" belongs to config.

[novking]

https://docs.aws.amazon.com/cli/latest/topic/config-vars.html#using-aws-iam-roles
i think that belongs to .aws/config

[rmtuckerphx]

Thank you for considering the pull request.

The Amazon docs seem to indicate that the role_arn and source_profile belong in the config file, but they definitely also work in the credentials file.

For my purpose (AWS CLI Configure extension for VS Code) I like supporting it in the credentials file so I built the extension from my modified fork.

Thanks for an awesome library. Makes Alexa development with ask-cli so much better!!

Thank you for your pull request. However, according to AWS doc (https://docs.aws.amazon.com/cli/latest/topic/config-vars.html#the-shared-credentials-file), your alt schema is not really valid. since this lib is supporting ASK CLI, i would like to follow their rule.