Collect request time, response time, user agent, remote addr and query params

- [x] Request time (via #5)
- [ ] Response time
- [ ] User agent
- [ ] Remote addr
- [ ] Query params
For remote addr, the headers to consider are

```
X-Real-IP
X-Forwarded-For
X-Forwarded-Proto
```

For request time, req has a field:
```
req->start_msec
```

For upstream response time, req has a field:

```
req->upstream->state->response_tim
```

And for user agent there's the header

```
user_agent
```