deploy: print last output line if no change in 10 seconds

Depends on #14. Merges #15.
If `deploy`'s output didn't change for 10 seconds, then print the last line of output to the chat.

```
Running 10 secs: <Last line of output>
Running 20 secs: <Last line of output>
Continuing...
```

Rename this to `DeploymentsMonitor`?