extract CachingSupplierRegistry from InjectorBackedRegistry
- also used in SpringBackedRegistry
add method for invalidating caches in CachingSupplierRegistry
add tests for equals and hashCode methods
introduce RegistryBacking interface and remove SpringBackedRegistry and GuiceBackedRegistry
Merge pull request #435 from lhotari/caching-supplier-registry-pr

extract Registry implementation from InjectorBackedRegistry and SpringBackedRegistry
Add test for BufferingPublisher Reactive-Streams TCK verification (#436)
Add a pull based publisher impl.
Fix BufferingPublisher Reactive-Streams TCK violations (#436)
Enable error state Reactive-Streams TCK verifications for BufferingPublisher (#436)
Fix codenarc issue
When buffering a publisher, don't pull on it until a request comes in from downstream.
minor test tweak.
Optimise the publisher bufferer by getting out of the way if the downstream subscriber wants to be firehosed.
implement equals and hashCode for CachingBackedRegistry
Add test for DefaultResponseTransmitter#transmitter Reactive-Streams TCK verification (#436)

Fix DefaultResponseTransmitter#transmitter Reactive-Streams TCK violations
Add test for WebsocketBroadcastPublisher Reactive-Streams TCK verification (#436)

Fix WebsocketBroadcastPublisher Reactive-Streams TCK violations
Wire the stream TCK tests into the build, but don't fail the build if they fail yet.
Minor improvements to the stream tests.
Make the buffering publisher pass the streams TCK.

Also enabled the TCK tests as they are now passing.
Use Guava's StandardSystemProperty enumeration when appropriate.