Add response time to each check output

[luiscoms]

Currently the output of each check is

{
    "status": "failure",
    "results": [
        {
            "output": "'NoneType' object has no attribute '__getitem__'",
            "checker": "throws_exception",
            "passed": false
        }
    ]
}

We want to append elapsed time of each check like this:

{
    "status": "failure",
    "results": [
        {
            "output": "'NoneType' object has no attribute '__getitem__'",
            "checker": "throws_exception",
            "passed": false,
            "response_time": 9999999999
        }
    ]
}