Improved heuristic for locale matching

[tohagan]

Thanks for this package, very useful and a nice simple clean interface.

Android 7.0 introduced a smarter heuristic for locale matching that searches child locales of a root language locale before trying a new language preference. Full details with samples are here ...

https://developer.android.com/guide/topics/resources/multilingual-support

Would be wonderful to support this improved algorithm in your pick() function.