3.1 (Now with better backwards compatibility)

The main changes here are that the transport layer has been separated from the client, so that Java 8 websocket clients can be used instead of the Java 11 javax websocket client/server: just import the connector you need and Maven/Gradle should work the rest out.

Additionally, the Error object now supports carrying exceptions thrown internally for much better debugging.

First public release

The interface is looking about right to me.
It needs more tests and doc, but perfect is the enemy of done and I want feedback sooner rather than later