Convert lang/lt.js to UMD
Convert lang/vn.js to UMD
Failing tests for moment.utc() returning null
Don't call .utc() if makeMoment() returns null
Merge pull request #1123 from adambiggs/umd-bug-fix

Bug fix for recent changes in moment.utc()
Merge pull request #1121 from mmozuras/feature/convert_lt_and_vn_to_umd

Feature/convert lt and vn to UMD