Detect Shared Dictionary Compression over HTTP (SDCH) support automatically

[diurnalist]

Google has put out a white paper describing a protocol for sending down content deltas.

If feasible, dynoSRC middleware should be able to respond to HTTP requests matching this spec and respond with appropriate deltas to let the client do the heavy-lifting itself.

[josheverett]

Would be extra cool if we could pair SDCH with AppCache: https://developer.mozilla.org/en-US/docs/HTML/Using_the_application_cache