Separate landing pages from the developer blog

[smashwilson]

The developer blog is by far the longest build that we run as part of this site; I've seen it take upwards of 30 minutes to complete. It's also the most failure-prone, because it uploads so many things that it's the most likely to hit Cloud Files problems and so on.

I have a few issues open already to address this at the platform level, but as a quick fix, we could easily separate the landing pages (/, /sdks, and so on) into a different, much smaller Jekyll repository.