I missed it when I first read the blog post, so I figure it's worth emphasizing: the new async/await support is only available on JavaScript engines that already support "function*" generator functions: Node 4, Firefox, and Chrome, but not Safari or IE/Edge.
Supporting async/await in ES5/ES3 is on the roadmap for TypeScript v2.0. https://github.com/Microsoft/TypeScript/wiki/roadmap