Ability to select which aws profile to use

[0xdevalias]

Currently it appears that badbucket will just use the default aws profile configured. It would be cool if we could specify which profile to use, like with the aws CLI tools.

If this feature is already implemented, it wasn't obvious how to use it from the output of -h:

⇒  badbucket -h
Usage of badbucket:
  -b string
    	S3 bucket name
  -bucket string
    	S3 bucket name
  -r string
    	AWS region
  -region string
    	AWS region