Redesign the landing page

[skryukov]

A new landing page, with a violet theme and Schibsted Grotesk (OFL). It's a draft until the placeholder phone screenshots are replaced with a real starter-kit recording, and its quick start links need #12.

A few copy questions for you:

• Should Hotwire be named on the homepage at all? You removed it in c979b75.
• Keep the "37signals uses it for HEY and Basecamp" line? Their site lists them as the makers, but doesn't say the apps use it.
• Is the violet brand colour OK site-wide, or only on the landing?