notifymyandroid plugin

The plugin sends a notification to your NotifyMyAndroid account whenever a player joins the server. It's basically a modified version of mdeneen's pushover plugin.

The config should look like this:
```javascript
        "nma_plugin": {
            "api_application": "StarryPy Server",
            "api_event": "Player joined",
            "api_key": "API_KEY",
            "api_priority": "0",
            "auto_activate": true,
            "ignored_players": [
                "Player"
            ]
        },
```

I hope I'm doing this right. I'm still a bit new to git, github and Python. ^^