Automate the process of generating a new Babel release report

[gaurav]

This would involve:

• Get the current and previous version from the user.
• Creating a new directory in releases/[version].
• Creating a new directory in releases/[version]/json and copying selected reports from our output files into it.
• Creating a new directory in releases/[version]/tables and copying the tables generated in PR Improved reports with tables #624 into that release.
• Generating a basic report in releases/[version] (ideally, by pulling changelogs from Babel) and including a diff from the previous version.
• Updating the previous release and releases/README.md to include the most recent version.
• Tag the version.

Probably a little script in scripts/ with some command line arguments would be ideal. It would also need some moving around of existing files.