ES6 transpiler: https://github.com/google/traceur-compiler/
Like before, we'll be working in the draw() function which is a common pattern in the D3 world. Everything in draw() gets removed and the function is plugged directly into the d3.json call.
A previously used json file is used in this screencast again. It is a basic json file that contains a title as well as a value. These values will be used to give each bar a percentage value