Improve: dictionary relationships

# The idea
```
NSDictionary *dictionary = [self.testUser hyp_dictionaryFlatten:YES];
```

# The result 
```
dictionary[@"notes[0].id"] =>  0
dictionary[@"notes[0].text"] => This is the text for the note A

dictionary[@"notes[1].id"] => 1
dictionary[@"notes[1].text"] => This is the text for the note B
```
Could we do `dictionary[key] = value`? or will that do `setObject` instead of `setValue`?