Moya upgrade

Fixes #33.

@orta: note that in https://github.com/AshFurrow/Moya/pull/49 , we now use `RACSignal.defer` in order to create signals and delay the side-effect of adding to our inflight requests cache. The bottom line here is that simply calling `Provider.request(.FeaturedWorks)` no longer kicks off a request. The signal that it returns is "cold", meaning that the work it represents (the network request) won't be started until it's subscribed to (either with `subscribeNext` or by binding it to some property. This is more idiomatic for ReactiveCocoa.