Export data from non-Gregorian calendars

Similar to #167, `ruby-cldr` currently only exports Gregorian calendar data, yet CLDR v41 has data for 16 different calendars.

Note: There are a [number of aliases](https://github.com/unicode-org/cldr/blob/86fd8773ed0f3c4da15be368d2ba3b5683ed9f93/common/main/root.xml#L1927-L1929) in the `root` locale that would need to be implemented if we start exporting the other calendar systems