Fairly major changes (new tink, asyncness, factories, inline auth)

 - Upgrade to new Tink, use more thoroughly
 - Async API compatibility. (Preparing for NodeJS + Client stuffs)
 - Factory class instead of create() method
 - InlineAuth, which initiates the session, and can start a new session based on username/password from params/http headers, and get it ready at the start of the request