include jspm package.json config

This configuration makes the module play a little more nicely with jspm - reducing the download time and ensuring the source is delivered minified with source maps.

See an example here of it being served over the CDN - http://jsbin.com/EHoyItAj/1/edit.

With the download tool, one would do `jspm install moment`.

Any questions just ask. Appreciated for the time to look into this.