Creating animated GIF files out of D3.js animations

I am creating D3.js animations, like this: Demo

Let's say I want to present my work here (or on a blog). About the best I can do is post a picture:

On the other hand, if I, let's say, use the Python library Matplotlib for data visualization, I could produce an animated GIF file, and post it here:

I would like to programatically obtain similar animated GIF files out of my D3.js animations. How can I do this?

NOTE: I started working on getting events from d3.transition(), but so far I didn't have any luck.