More closely following the AWS SDK environmental variables

I noticed that `collect` failed in an environment where e.g. `aws sts get-caller-identity` worked. There are two factors:

1. collect looks for `AWS_REGION` but the value typically used is `AWS_DEFAULT_REGION` (see https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-envvars.html): https://github.com/duo-labs/cloudmapper/blob/ceebed149f9d86f8c9db17f3633fe6da0bf43436/commands/collect.py#L211

2. collect does not check the `AWS_PROFILE` environmental variable so anyone using a non-default profile will have failures unless they specify `--profile` as well.