Now supporting 'comment' text from STDIN

• Added the ability to pipe in the comment text from STDIN. Useful when another script generates the comment text.

Added 'comment' command and object storage integrations

• Added the ability to comment on a pull request (by PR number or commit).
• Implemented both S3 and Swift object storage backends for uploading files.
• Allow for automatic expiration of uploaded files to clean up the object store after a period of time.
• Added the ability to override the default comment template with a local file.

Initial release including 'status'

Initial release of the upr tool which currently only supports updating the status of a PR (based on its commit).