Added spring-messaging module with ReactorSubscribableChannel implementation based on Reactor's Processor component.

Also updated Gradle version to 1.7
Reorganized reactor-spring-context module since most of its functionality went into Reactor core.
Added PromiseHandlerMethodReturnValueHandler to enable returning Promises from Controller methods in Spring MVC.
Drastically reduce throughput test iterations for CI servers.
Tweaked gitignore