Enhancement: new Chronology for International Fixed Calendar

Hello joda-time stakeholders

Managed to implement a 13 month x 28 days a month calendar from the previous century, cf. https://en.wikipedia.org/wiki/International_Fixed_Calendar

Working with zones is broken, see TestInternationalFixedChronology lines 99 - 103.
InternationalFixedChronology#getInstance (DateTimeZone zone) does not properly work yet.

Any idea how to fix this ?