Clean up the site's CSS and HTML

This branch does a few things to clean up the site's CSS and HTML:

- Any `style` attributes on HTML nodes have been moved into CSS files
- Map styles have been consolidated into a single file, separate from the main CSS for the site
- HTML has been cleaned up, removing things like empty spacer dives and making it more semantic
- Moved all third party dependencies into a `vendor/` folder, leaving `assets/` for files we've created
- Normalises CSS formatting and removes commented out styles
- Automatically hides the address bar when viewed on an iPhone