Link to tagtree 'Thinking in React' video - on master

I've created a high quality tagtree.tv screencast that conveys the principles of the awesome 'Thinking in React' guide while building a simple app similar to the one in the guide.

The link to the screencast: http://tagtree.tv/thinking-in-react

It's been popular so far with limited exposure, and I think Reactors will enjoy and derive benefit from it.