Case-insensitive

I've recently been working on some form validations and wanted to use the PhoneNumber validator class in my input filter and realized it would be awesome if we could set the country case-insensitive :)
Merge branch 'patch-2' of https://github.com/BruceLampson/zf2 into hotfix/5892
Added unit test for PR #5892
Merge branch 'hotfix/5892'