Andrew Mohrland

I _think_ the semantics of this is correct: we want to use the blocking pool to enqueue the request and to register the continuation we're passed, and I think that's...

I've updated this to instead use `interruptible(many = false)`, since `Producer#send` [respects thread interruption](https://kafka.apache.org/28/javadoc/org/apache/kafka/clients/producer/KafkaProducer.html): > InterruptException - If the thread is interrupted while blocked

Since this is new and introduces some risk, I'm going to wait till we've determined that ce3 is stable in prod before merging.

These run fine locally, but fail on Travis. My guess is that this is due to port conflicts between the still-running docker-compose that we use for the other tests.

Also, amusingly, I needed to remove the `examples` build, to compile the project. For some reason, changes to tests in `core` caused `RecordFormat`s to not be found in the examples....

A blast from the past