Export decimal number patterns for all plural forms

Currently ruby-cldr exports only one of the plural forms for each decimal format pattern. That makes it impossible to properly format numbers in languages like Russian where nouns might have multiple plural forms. See twitter/twitter-cldr-rb#129 for a more detailed explanation.

Unfortunately this change isn't backward compatible. Not sure how you do versioning for ruby-cldr, but this change might require a new major (or at least minor) version.