Road to publish

[ifosch]

These changes are solving issues identified during our first episode published using the toolkit.

• Dependencies were updated
• Make appu use directories to access external files: The appu container needs some files to be provided for running, like config.cfg, AWS credentials, or the logo image. These were originally mounted as files, but this seems not to work well from the Go Docker SDK, so this is now using directories and volumes definitions.
• Make appu accept S3 URLs to download the master: This provides another way of retrieving the master recording when running appu. Using S3 is easier than adding another file sharing service with authentication.
• Include links into the episode's description in the feed
• Add README.md: This provides more context and guidance for using the toolkit.

[ifosch]

These failing tests are my fault. I'll look into fixing these next.

[ifosch]

I finally got this fixed by including an empty files directory for the appu Docker image. Fixing it in a better way would imply fixing the Python tests in a better way, but I decided not to do so as we are considering to remove the code.