Extend "json_path" config option with JSONPath parser for deep nested data

[TyShkan]

Followup to #16

It would be quite helpful to parse more complex JSON-files, especially if it's http-responses from some API.

With actual JSONPath parser it could be done quickly and clean with a simple expression like response.data[*] applied to

{
  "response": {
    "data": [
      { "name": "row one", "key": 42 },
      { "name": "row two", "key": 43 }
    ]
  }
}

would return

[
  { "name": "row one", "key": 42 },
  { "name": "row two", "key": 43 }
]

which is the form of the data expected as input for the json format.

The same library is used by Meltano Singer SDK.