[bot] Setting status message to git commit hash doesn't work in Docker container

[RalphORama]

Description of the Bug

docker build doesn't include the .git directory, so git rev-parse --short HEAD fails when trying to set the bot's status message. One possible solution is to move Docker builds to Travis, then use docker push so we can use Travis to set default environment variables for the image

Steps to Reproduce the Bug

1. Launch the bot using the Docker container (ralphorama/santabot)
2. Watch log output

The Bug Affects

• [x] The Discord Bot
• [ ] The Database or API
• [ ] Other program functionality (.env, scripts, etc.)
• [ ] Documentation
• [x] Containerization
• [x] CI
• [ ] Other: