Terminating Judo does not terminate the already-running script

Simple to observe, prepare a script:

```shell
#!/bin/sh
echo a > /tmp/a
sleep 10
echo b > /tmp/a
```

Run, interrupt without waiting 10s, wait 10s, observe contents of /tmp/a.

I think this could be solved by allocating a PTY (`ssh -t ...`), but this probably means we'd have to do a bit of terminal emulation? See also #18
