Add -v flag that causes fs events to be logged

Helpful for hunting down unexpected restarts (in my case, flymake's the culprit).

```
2013/11/24 01:21:37 file changed: "web/flymake_users.go": CREATE
2013/11/24 01:21:37 file changed: "web/flymake_users.go": DELETE
2013/11/24 01:21:37 terminating command 897
2013/11/24 01:21:37 running go build && ./server config.json
2013/11/24 01:21:45 file changed: "web/users.go": MODIFY
2013/11/24 01:21:45 terminating command 1596
2013/11/24 01:21:45 running go build && ./server config.json
```