This PR adds appropriate corrections to certbot dockerfile to work with the new layout (moving certbot python project in its own subdirectory).
This PR has been tested with success using the `build.sh` script on a fake v1.0 version of certbot published on my fork (https://github.com/adferrand/certbot/releases/tag/v1.0) instead of archives from `certbot/certbot`.
Certbot is EFF's tool to obtain certs from Let's Encrypt and (optionally) auto-enable HTTPS on your server. It can also act as a client for any other CA that uses the ACME protocol.