v0.5.3

Expand flatten_dict into flatten_json.
flatten_json flattens lists as well as dicts by default.

Examples:

        {
            "key1": {
                "key2": "value"
            }
        }
        turns into
        {
            "key1.key2": value
        }


        {
            "key1": {
                "key2": [{
                    "key3": "foo",
                    "key4": "bar"
                }, {
                    "key3": "baz"
                }]
            }
        }
        with flatten_lists=True, turns into
        {
            "key1.key2.key3": ["foo", "baz"],
            "key1.key2.key4": "bar"
        }