Cleanup headings on landings

[sapegin]

• Wrap whole book (page) title in h1
• Keep page outline more consistent and semantic
• Fix testimonials layout
• Add styles for hr

Part of #109

Closes #86

[bebraw]

Let's go with this. I'm thinking we should integrate the "hire me" bit to each book page (upsell workshops etc.) but that's something for me to figure out. 👍