Language Variant File Names should be aligned with ISO 3166

[vanthome]

This ISO standard defines country codes in capitals:
http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
Also this standard defines language tags in the form de-AT or en-GB etc.
http://en.wikipedia.org/wiki/IETF_language_tag

Therefore, I think the files in the lang folder should be renamed to mach this form.
Currently we have en-gb.js but this should be en-GB.js

[ichernev]

@timrwood there was a discussion about that some time ago, but I can't dig it up. What was your stand?

[timrwood]

I think we should treat language identifiers as being case insensitive and replace _s with -s.

While language codes should technically have capitalized modifiers, it makes it easier for node to require languages in a consistent naming pattern.

For reference, here are some examples of different valid language identifiers from CLDR.

http://unicode.org/cldr/utility/languageid.jsp

en
eng-840
pt_PT
AZ-arab-Ir
zh-Hant-HK
en-cmn-Hant-HK
sl-Cyrl-YU-rozaj-solba-1994-b-1234-a-Foobar-x-b-1234-a-Foobar

I opened an issue at #963 to track this as well.

[icambron]

Fixed by #985. All of these are now accepted:

moment.lang('en-gb');
moment.lang('en-GB');
moment.lang('en_GB');
moment.lang('EN_GB');

[mattjohnsonpint]

nice!