Export territories containment data from CLDR

The data is exported in the following format: 

```yaml
territories:
  001:
    contains:
      - 019
      - 002
      - 150
      - 142
      - 009
  002:
    contains:
      - 015
      - 011
      - 017
      - 014
      - 018
```

For more information see the [docs](http://www.unicode.org/cldr/charts/25/supplemental/territory_containment_un_m_49.html). I also wanted to include territory names into the export, but, unfortunately, this data is only available in the comment above each XML node in `territoryContainment` section, so it's kinda tricky to extract it and I'm not sure if it's gonna be there in future versions of CLDR.