Improve: Relationship dictionary representation

### Convert
```objc
NSDictionary *dictionary = [user hyp_dictionary];
```
### From
```json
"notes": [
  {
     "id": 1,
     "text": "This is the text for the note 1"
  },
  {
     "id": 7,
     "text": "This is the text for the note 7"
  },
  {
     "id": 14,
     "text": "This is the text for the note 14"
  }
];
```
### To
```json
"notes": [
  {
    "0": {
      "id": 1,
      "text": "This is the text for the note 1"
    },
    "1": {
      "id": 7,
      "text": "This is the text for the note 7"
    },
    "2": {
      "id": 14,
      "text": "This is the text for the note 14"
    }
  }
]
```