Log deploy, set force_checkout

### Log deploy

Use git log to log the deployment to logger

```
git log -1 --format='Deployed nbviewer %h %s'
```

At first glance I didn't see a way to send to syslog or rsyslog through states. Additionally, the git module had no git.log command, so I just used cmd.run.

### Force checkout

Force a checkout even if there might be overwritten changes