Fixed the conversions of unsigned integer types.

This release welcomes @Sebmaster to the team, as he revives the project in service of jsdom.

The backward-incompatible change is moving away from pure ES2015 source code, instead using the subset supported on Node.js 4.0. That does not include ES2015 modules, so the consumption strategy moves to normal CommonJS modules.

Additionally, he implemented the following conversions:

• All numeric types, although the float implementation is a bit sketchy
• A { treatNullAsEmptyString: true } variant for DOMString
• ByteString
• Date
• RegExp
• USVString (!)

Added "traceur-runner": true to package.json, to better work with traceur-runner.

Added void.

Added double.

Made the package use the es6ify transform when used with browserify.

Initial release, with boolean and DOMString as the only supported conversions.