Fix bool support

[davdr]

This fixes parsing of boolean values.

Boolean support was added thanks to #17, but was incomplete. Consider the following example JSON:

{
    "counter": 1234,
    "values": [
        {
            "id": "id-A",
            "count": 1,
            "some_boolean": true,
            "state": "ACTIVE"
        },
        {
            "id": "id-B",
            "count": 2,
            "some_boolean": true,
            "state": "INACTIVE"
        },
        {
            "id": "id-C",
            "count": 3,
            "some_boolean": false,
            "state": "ACTIVE"
        },
    ]
}

This previously yielded a "skipping not numerical result" error.

This PR corrects this, and also updates the example and README to demo the boolean parsing.

/cc @WilliButz

[SuperQ]

LGTM, Thanks