0.2.0

• Refactored app as a package in quetzal.app.
• Added a file storage backend, an alternative storage that does not use Google
  Cloud Platform.
• Added Let's encrypt SSL certificate management.
• Added deployment on GCP documentation.
• Added Sphinx documentation structure.
• Added file delete endpoint.
• Added file state in base metadata.
• Added a simple.naive implementation to file delete.
• Added a simple/naive workspace commit conflict detection.
• Added global queries.
• Added support for temporary files. They are uploaded on the users' bucket.
• Added path as query parameter when uploading files.
• Fixes unit tests that failed since introduction of roles.