Expose different module specs

[gmarty]

Currently the code is only exposed as a commonjs module which makes sense on Node, but is not optimal on the browser.
That'd be great to expose it under different module specs too. Something like UMD can be used to increase compatibility and support more environments.

[camertron]

Hey @gmarty, you should be able to use twitter-cldr-js (or probably more likely twitter-cldr-npm) in the browser without too much trouble. We expose a commonjs module if module.exports is defined, otherwise we define a top-level object called TwitterCLDR on this, which is window in the browser. Could you explain why such an approach is not optimal? Is the concern adding something to the global namespace? What would you suggest to improve things?

I'd happily accept a pull request adding support for other module specs such as the ones described in UMD. Viva la open source.