Accept int as map key too

Accept integers in severity map too since when you pass the following

    "text": {
        "type": "text",
        "include": "(\\.*)",
        "severity": {
            "3": "advice"
        }
    }

to `.arclint` it throws an error. Reason is `json_decode` or PHP itself implicitly casting `"3"` into an integer `3`.