should expose the data about presence in the Knesset (נוכחות במשכן)

```bash
>>> from knesset_data.html_scrapers.mks_presence import MksPresence
>>> mks_presence = MksPresence.get()
>>> next(mks_presence)
{"mk_id": 909, "mk_name": "עבדאללה אבו מערוף", "present": True, "is_mk": True},
>>> next(mks_presence)
{"mk_id": 1: "mk_name": "יולי יואל אדלשטיין", "present": False, "is_mk": True},
>>> next(mks_presence)
{"mk_id": 41, "mk_name": "אריה מכלוף דרעי", "present": False, "is_mk": False}
```

* the data is available here: http://www.knesset.gov.il/presence/heb/PresentList.aspx
* there is code in open knesset which does it, but maybe it's better to write it from scratch, I suggest to use pyquery and requests library - it should be easy

Inizia dal punto di ingresso MksPresence indicato nell’issue ed esamina la pagina delle presenze della Knesset all’indirizzo http://www.knesset.gov.il/presence/heb/PresentList.aspx. Esamina l’implementazione esistente di Open Knesset per avere il contesto, quindi fai in modo che MksPresence.get() esponga record con i campi mk_id, mk_name, present e is_mk conformi agli esempi.

Scritto dal modello di indicizzazione a partire dal testo della issue.