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...
```

It's absolutely ok to remove all the listeners because
- At this point we don't them. The deployment is going to be purged away.
- We absolutely control the lifecycle of deployment, so no third-parties are going to suffer from this.