Update to support requirejs in the browser, no functional changes

[owenallenaz]

This wraps the existing diacritic index.js in a UMD boilerplate from https://github.com/umdjs/umd . This allows people to utilize diacritics in the browser via requirejs. The merge diff likes a nightmare but that's because it increased the indent level by 1 due to the wrapper. I didn't change any of the code inside the wrapper if you delete the wrapper and undo the indent you'll see no changes. It will continue to function in Node as it did before.

[andrewrk]

Why is this required? I've been using this module in the browser for years without this boilerplate.

[owenallenaz]

If you are using this in the browser you must be wrapping it or copy-pasting it into a different file. module.exports is not something which is available in browsers so I don't see how you could do a standard <script src="/node-diacritics/index.js"></script> and have it work properly?