Merge branch 'hotfix/empty-private-repos'
Refactor the endpoint for list S3 files
Refactor the S3 url builder to use url_for functions
Merge branch 'master' of https://github.com/CenterForOpenScience/osf into hotfix/s3-keys
Allow for nested paths
Update tests
Naming fix for nested folders
Use rstrip rather than ifs h/t @sloria
Merge branch 'develop' of https://github.com/CenterForOpenScience/osf.io into hotfix/s3-keys

Conflicts:
	website/addons/s3/utils.py
Merge branch 'hotfix/0.21.14' into develop