Support environment variables for AWS Region and AWS Endpoint override

[tmspzz]

Enhancement Suggestion

Add  support for environment variables for AWS Region and AWS Endpoint override 

Steps which explain the enhancement or reproduce the bug

1. Read the AWS_REGION variable from the environment
2. Read the AWS_ENDPOINT variable from the environment
3. Use them when communicating with relevant AWS services (S3 or the like)

Current behavior

Rome does not support environment variables for AWS Region and AWS Endpoint override 

Suggested behavior

Rome should read AWS_REGION and AWS_ENDPOINT from the environment

Why would the enhancement be useful to most users

Not everyone want to use a file for this

Rome version:

>= 0.14.x.y

OS and version:

MacOS Sierra

[tmspzz]

Done