ListRequest to iterate over the files in a bucket
Merge pull request #24 from arthurdarcet/list-request

ListRequest to iterate over the files in a bucket
Added MIT license
Added a license for pypi
Add support for buckets retrieval.
Remove unneeded parameters
Add get_bucket_objects feature, TODO(add/fix tests)
Fix get_bucket_objects()
Add extra headers when listing the bucket keys
Make extra params work as expected
Fix tests and remove unneeded method.
Add tests for get_bucket_objects()