Add back support for --endpoint-url option to s3
Update S3 unit tests for endpoint_url param
Add unit test to ensure endpoint-url is passed to botocore for s3
Update ls to support endpoint-url
Merge branch 'mguillaume-develop' into develop

Closes #469

* mguillaume-develop:
  Update ls to support endpoint-url
  Add unit test to ensure endpoint-url is passed to botocore for s3
  Update S3 unit tests for endpoint_url param
  Add back support for --endpoint-url option to s3