Add script to start app; add README
Install webpack via npm for development only

During development, I'll run a webpack process to keep the processed
assets updated, and eventually set up a git hook or something to run the
build before every deploy for live apps.
Build the JS assets with webpack

This adds a very basic webpack.config with settings that will allow
easily splitting out bundles later.

Next steps (relating to configuring webpack):
 - set up ES6 parsing
 - set up JSX parsing
 - try out serving styles with webpack