Minor tweak.
Fixes #317 Changes NetChannel.close() return to Promise<Boolean>
Update gradle wrapper.
Add a method to Promises to provide a single-use style Consumer by attaching a special Consumer that fulfills a Promise when the given Composable publishes the next value.
Change SingleUseConsumer to use CAS operations instead of a synchronized block that was insufficient to prevent a race condition when multiple threads publish values at the same time.