Added Serenade.js example

So this took me *way* too long, but here, finally, is a todomvc implementation with Serenade.js. I've gone through the specification a couple of times, and I think I have everything in place, let me know if I made any mistakes.

One thing I'm not sure about is that the specification mentions a list of browsers that need to be supported, but the link is broken. Since Serenade doesn't support IE8 or below, obviously the app is not going to work there. Not sure if that's a problem.