Remove embedded "express" and "ejs" modules

Let's rely on installing them using "npm" instead.
Prepare the website to run on the new server

  * Update code to run with the current version of Express.

  * Get rid of now useless pegjs-website script.

  * Create pacakge.json listing all the dependencies. This makes it possible to
    install them using "npm install".

  * Add the "tmp" directory. This is needed for the restart.txt file used by
    Phusion Passenger, which runs the website in production.

  * Update README.md.