* renamed @ModuleChannels to @Bindings
* moved Source, Sink, and Processor to the `org.springframework.cloud.stream.messaging` package
* updated documentation
Standard channel interface types of Sink, Source, Processor
are provided, but user can create others with @Input and
@Output MessageChannel methods.
To get the declared channels in an app you can use the
@ModuleChannels qualifier to inject the interface, e.g.
@ModuleChannels(Cafe.class) injects the channels defined
in the Cafe.
