Update the tutorial. BUG: Code in <script> tags is invisible.

Hey, Shailen. These are the changes I've made to update the tutorial. Unfortunately, code snippets aren't (for the most part) showing up, and the few that are (because they use `<pre>`, not `<script>`) aren't pretty printed.

In the earlier pages, the code probably has the wrong indentation, so I'll need to fix that.