Xcode subproject

Chute SDK should live in its own project. Dragging all files as-is is a pain in ARC-enabled projects.

Installation instructions are pretty much the same as [RestKit's](https://github.com/RestKit/RestKit/wiki/Installing-RestKit-in-Xcode-4.x), except user header search paths is **"$(SRCROOT)/Chute-SDK/iOS"**.