pushover support

You need to add something like this to your plugin config:

        "pushover_plugin": {
            "api_key": "MY_API_KEY",
            "ignored_players":
                "Player1",
            ],
            "user_key": "MY_USER_KEY"#
        }
Merge branch 'pushover' of https://github.com/mdeneen/StarryPy_plugins into pushover