Handler still does internal filtering

[asachs01]

{
    "timestamp": "2018-11-19T16:22:34.639264-0600",
    "level": "info",
    "message": "handler output",
    "handler": {
        "type": "pipe",
        "command": "/opt/sensu/embedded/bin/handler-mailer.rb",
        "name": "mailer"
    },
    "event": {
        "id": "ae98f83c-976f-494d-9dea-823cd20b9d18"
    },
    "output": [
        "warning: event filtering in sensu-plugin is deprecated, see http://bit.ly/sensu-plugin warning: occurrence filtering in sensu-plugin is deprecated, see http://bit.ly/sensu-plugin only handling every 60 occurrences: sensu.sachshaus.local/testing_error"
    ]
}

^ seems to indicate that this plugin still does internal filtering a la the "handling every 60 occurrences". Ideally, this would use the newer version of the sensu-plugin gem (iirc, it's at 2.7.0). I know the current way to do things is to use refresh, but this seems to be an unnecessary step when bumping up the version fixes the issue. I see there's already been #45 and #26 discussing the issue, but not the fact that there does appear to be filtering behavior present and active inside the plugin. I'll submit a PR shortly to remedy the issue.