Add support for AWS profiles (deploy)

[landonreed]

When deploying to S3 buckets on various AWS accounts a mastarm user must update .aws/credentials so that the default credentials point to the correct AWS account. It would be great to just pass a --profile fdot arg to indicate to mastarm that it should use alternative credentials for S3 deployment rather than having to make this manual switch.

This docs page appears to provide info on how this might be done: https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/loading-node-credentials-shared.html. It also notes that the env variable AWS_PROFILE can be used to set the profile that should be used.