exposes cities directly from Country

[chriys]

Add the ability to get all cities within a country tested with small country like Maldives. although not included in tests it was also tested with Luxembourg. For now it only return an array. A collection is coming soon.

[janisblaus]

@dusterio hi Denis, could this PR be merged into main package?

[dusterio]

@janisblaus good idea, but would be nice to return a collection for consistency purposes?