Fix IETF language tag lookup
Fix IETF language tag lookup

The IETF specification says the language tags should be treated as
case insensitive (see http://tools.ietf.org/html/bcp47#section-2.2.1) so
we have to discard the case when saving the languages and performing the
look-ups.

foretagsplatsen/numbro,MeteorPackaging/Numeral-js,prantlf/numbro,Kistler-Group/numbro,danghongthanh/numbro,atuttle/numbro,Stillat/numeral.php,matthieuprat/numbro,atomlipetsk/Numeral-js,adamwdraper/Numeral-js,rafde/numbro,spalger/numeral-js,clayzermk1/numbro,BenjaminVanRyseghem/numbro,stewart42/numbro