Cldr Messages version 0.12.0

Enhancements

The primary focus of this release is gettext integration. The effort is kindly driven by @maennchen and the majority of the work is his.

• Add Cldr.Message.format_to_iolist/3 which formats a binary message into an iolist. This helps with incrementally binding placeholders where some may be bound at compile time and others at runtime. It also makes integration with gettext simpler since this function returns a list of completed bindings and a list of bindings that were not found.

• Adds an implementation of Gettext.Interpolation to support gettext integration.