Refactor the library away from having a single global client, but provide a client of our own that the user of the library is responsible for. This means that the user has control over the allocation and destruction of the client. This solves issue #60 and is enabled due to tireless work by shepmaster. Big thanks!
Small fix to the public interface of sync::ObjectClient that was not properly sync.
Fix urlencoding url paths correctly in several places.
Update cloud storage to use the new url, www.googleapis.com => storage.googleapis.com
@pseguin2011: Implemented a configurable authentication layer through the TokenCache trait.
Implement customisable authentication providers, via the Client::with_cache method.