Consider URI syntax for transports

[codefromthecrypt]

From https://github.com/yschimke/oksocial/pull/255#issuecomment-317329218

From @yschimke:

Generally seems like having a URI for the Zipkin sink would be a useful feature for Brave. e.g. https://github.com/rsocket/rsocket-java/blob/1.0.x/rsocket-core/src/main/java/io/rsocket/uri/UriTransportRegistry.java

Personally, I've thought about this sometimes. It can work provided there's no endpoint doing weird things like requiring query params. Seems also similar to guava cachebuilderspec