Auto checkout merge requests

Do @tildes mr=X where X is the merge request number from tildes-community/tildes-cf to pull the MR from GitLab and restart the following services:

• gunicorn.service
• 'consumer-*.service'

This does not yet handle alembic or other changes but this is an okay starting point.

It may take up to a minute to apply, the script uses a cronjob and checks every minute for new mentions. And it only handles the latest mention.

Do @tildes master to checkout back to master.

Approved users that can use this:

• bauke
• talklittle
• cfabbro
• deimos

! ! ! Temporarily Unavailable

I'm an idiot an accidentally deleted the code for this while migrating the server to use the tildes/tildes staging branch. x) I'll remake this at some point :D