Format nested response keys

[chriswhong]

Response keys that have a parent defined in the layout CSVs should become keys in an object that gets returned as the parent's value.

...
  'LION KEY': '1311500290',
  'LION Borough Code': '1',
  'LION Face Code': '3115',
  'LION Sequence Number': '00290',
...

should become:

'LION KEY': {
  'LION Borough Code': '1',
  'LION Face Code': '3115',
  'LION Sequence Number': '00290',
}