Add a simple tests, verify JSHint pass on build, use es6-promise#polyfill etc.

Had some free time this morning so used to have a browse through a few of the `next-*` repos.

- Use `es6-promise#polyfill` method so that `GLOBAL.Promise` won't accidentally get overwritten multiple times.
- Set up a very basic test (happy to change this to jasmine if that is preferred but Jasmine wouldn't work out of the box for me :-/)
- Format `readme.md` code sample with javascript syntax highlighting.