Uses webpack to transpile sidebar.jsx into JavaScript to render the Sidebar component, which is currently a pure React component (i.e. stateless).
In addition to adding React and ReactDOM deps, I added the following devDeps:
* babel-core: Library to do the transpilation
* babel-loader: Enable transpiling using Babel via Webpack
* babel-preset-env: Compiles ES2015+ down to ES5
* babel-preset-react: Compiles JSX to JS
Bianca Danforth