Allow creation of moment+langs.js

Represents a continuation of #973 (didn't mean to create a new pull request specifically, but all the old work was made irrelevant anyway, and apparently github auto-closes pull requests if you delete the branch.  Go figure).

```moment+langs.js``` is a version of moment.js, prepackaged with all languages.  Can specify ```--embed_languages=ar,br``` to create ```min/moment+customlangs.js``` with just those two languages (went with this over ```min/moment+ar+br.js``` since it was easier to configure; could switch over if that's still your wish).  Also didn't indent the lang closures, since I think the file is readable as is; again, could indent if you guys want.

If you're wondering about ```lang/da.js```, that was just a minor tweak so that it would match the replacement regex and pass jshint.  And the error message is mostly in reference to ```lang/hr.js```, which at this time has the old node-require instead of a UMD wrapper, giving example output of:

```Warning: all language files must use the common UMD wrapper pattern.  Failed language file: lang/hr.js```