The only thing we need from ghost is the GZIPHandler. The
gorilla/handlers package has a CompressHandler, and much fewer
dependencies. Also, add a test that attempts a request with
an Accept-Encoding: deflate header.

RemoteAddr again.

Also removed some unnecessary duplication of code from net/http.

* Track ModifiedIndex, preventing missed updates
* Properly handle errors in presence protocol

Ensure that the Syncer listens on all interesting updates (added
compareAndSwap and compareAndDelete).

Previously the Controller would be left in a bad state on a master ->
slave transition.